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PROJECT PERIODIC REPORT

Grant Agreement number: 213390

Project acronym: PHOME

Project title: Photonic Metamaterials

Funding Scheme:

Periodic report: 1st □ 2nd X□ 3rd □ 4th □ Period covered: from June 1, 2009 to May 31, 2010

Name, title and organisation of the scientific representative of the project's coordinator1:

Costas M. Soukoulis, Professor, IESL-FORTH, Heraklion, Crete, Greece

Tel: +30 2810 391303 & +30 2810 391547

E-mail: soukouli@iesl.forth.gr

Project website2 address: http://esperia.iesl.forth.gr/~ppm/PHOME/

1 Usually the contact person of the coordinator as specified in Art. 8.1. of the grant agreement 2 The home page of the website should contain the generic European flag and the FP7 logo which are available in electronic format at the Europa website (logo of the European flag: http://europa.eu/abc/symbols/emblem/index_en.htm ; logo of the 7th FP: http://ec.europa.eu/research/fp7/index_en.cfm?pg=logos). The area of activity of the project should also be mentioned.

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Declaration by the scientific representative of the project coordinatorError:Reference source not found

I, as scientific representative of the coordinatorError: Reference source not found of this project and in line with the obligations as stated in Article II.2.3 of the Grant Agreement declare that:

The attached periodic report represents an accurate description of the work carried out in this project for this reporting period;

The project (tick as appropriate):

+ has fully achieved its objectives and technical goals for the period;

□ has achieved most of its objectives and technical goals for the period with relatively minor deviations3;

□ has failed to achieve critical objectives and/or is not at all on schedule4.

The public website is up to date, if applicable.

To my best knowledge, the financial statements which are being submitted as part of this report are in line with the actual work carried out and are consistent with the report on the resources used for the project (section 3.6) and if applicable with the certificate on financial statement.

All beneficiaries, in particular non-profit public bodies, secondary and higher education establishments, research organisations and SMEs, have declared to have verified their legal status. Any changes have been reported under section 5 (Project Management) in accordance with Article II.3.f of the Grant Agreement.

Name of scientific representative of the CoordinatorError: Reference source not found: Costas M. Soukoulis................................

Date: ............10/ .....June/ 2010............

Signature of scientific representative of the CoordinatorError: Reference source not found: ...

....................

3 If either of these boxes is ticked, the report should reflect these and any remedial actions taken.4 If either of these boxes is ticked, the report should reflect these and any remedial actions taken.

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Declaration by the scientific representative of the project coordinator1.............................................2Publishable summary.......................................................................................................................31. Project objectives for the period................................................................................................42. Work progress and achievements during the period.................................................................53. Deliverables and milestones tables..........................................................................................214. Project management................................................................................................................225. Explanation of the use of the resources...................................................................................236. Appendices..............................................................................................................................26

Publishable summary

The field of electromagnetic metamaterials is driven by fascinating and far-reaching theoretical visions such as, e.g., perfect lenses, invisibility cloaking, and enhanced nonlinearities. This emerging field has seen spectacular experimental progress in recent years. Yet, two major challenge remains: (i) realizing truly low-loss metamaterial structures. Linear gain inclusion in lossy metamaterials may provide a solution. (ii) Realizing true 3D metamaterial structures that will give negative n in different directions. Direct laser writing (DLW) may provide the solution of 3D isotropic metamaterials.

In the theory/modeling domain (WP1) we developed/improved various modeling tools: we extended the Finite Difference Time Domain (FDTD) code to lossy and to dispersive materials, we developed an inversion of the scattering data procedure, which enables to extract effective parameters (ε and μ) from the transmission data for chiral metamaterials, and we pursued the Microwave Studio, and FEMLAB commercial software, which gives the ability to treat very thin metals. In addition, we set out to take a systematic approach towards self-consistent calculations (using the semi-classical theory of lasing) for realistic gain materials that can be incorporated into or close to the NIMs, to reduce the losses at THz and optical frequencies. We developed, implement and used our own FDTD code to treat the field propagation and non-linear response of the gain material by coupling a set of auxiliary equations for the polarization oscillators and rate equations to the source-free Maxwell equations. Using FDTD simulations we studied the compensation of spatially distributed loss of metamaterials by differently spatially distributed inclusions of non-linear gain for 2D model systems.A lot of simulations were made, with aim to find new 3D interconnected designs that can be fabricated by directed laser writing by our experimental partners. We have new blueprints for bulk connected photonic metamaterials and new chiral metamaterials that give negative index of refraction. Our experimental partners have fabricated and characterized chiral metamaterials at GHz, THz and telecom wavelengths. Finally, using transformation optics, various plasmonic structures have been designed and studied analytically, whereas, until now, only the numerical tool was available for the study of such plasmonic devices. Novel physical insights have been provided regards the resonant behavior of these nanostructures and the nanofocusing properties that can be expected with nanoparticle dimers. These nanostructures exhibit considerable nanofocusing capabilities: our theory predicts a field enhancement that can go beyond a factor of 104 over a broadband spectrum.

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On the fabrication domain (WP2), as proposed, we have fabricated planar and non-planar new chiral metamaterials that give negative n at GHz frequencies. We have fabricated chiral metamaterials at THz frequencies and telecom wavelengths (1.5 micron). The telecom design is composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps with intermediate planarization via a spin-on-dielectrics. We have fabricated a bulk photonic metamaterial with direct laser writing (DLW). DLW can be viewed as a 3D analogue of electron-beam lithography. Fabrication of polymer structures by this approach is standard. Infilling or coating of such polymer structures with metals is not standard at all. We have pursued chemical vapor deposition of silver and also infilling with gold with electroplating, and we were successful in both these two techniques. Coating approaches using chemical vapor deposition have successfully been developed. More recently, infilling with gold using an electroplating approach has turned out to be highly attractive. This work can be viewed as a possible first “real-world” application of the far-reaching concepts of electromagnetic metamaterials.

On the characterization and testing task (WP3): We performed a large number of free space transmission measurements in the 10 GHz, and 30 GHz regimes, using all our 1D and 2D fabricating structures, with both planar and non-planar chiral metamaterials. In the experiment, HP 8364B network analyzer with two Narda standard horn antennas measures the transmission coefficient. Four linear transmission coefficients, Txx, Tyx, Txy, and Tyy, are measured and the circular transmission coefficients, T+ +, T− +, T+ −, and T− − are converted from the linear transmission coefficients. Using the standard definitions of the polarization azimuth rotation, =[arg(T+ +)−arg(T−

−)) /2, and the ellipticity, = 0.5 arcsin{(|T+ +|−|T− −|)/(|T+ +|+|T− −|)}, of elliptically polarized light, we calculate the polarization changes in a linearly polarized wave incident on the cross-wire structures. We have used the numerically develop a retrieval procedure adopting the uniaxial bianisotropic model to calculate the effective parameters, , and n- and n+, of the chiral metamaterial design. We prove the existence of the negative index originating from the chirality of the cross-wire metamaterial. As a comparison, the non-chiral version of the cross-wires pair design does not show any negative refractive index. We have optically characterized the chiral structures in the visible and near infrared and in the mid-infrared with circularly polarized incident light. Our measurements did not produce negative n at these high frequencies, but the strong optical rotation exists. Finally, we have fabricated and measured by THz spectroscopy the dynamic response of metamaterials, which give blue shift tenability and broadband tenability.

As promised, we created a web page for our consortium. The URL site ishttp://esperia.iesl.forth.gr/~ppm/PHOME/

1. Project objectives for the periodThe photonic metamaterials (PHOME) project has three scientific work packages (WP) and two extra ones, which are not scientific.

WP1 deals with the modeling and the theory of photonic metamaterials (PMMs). Leader: FORTH

WP2 deals with the fabrication of photonic metamaterials (GHz to THz). Leader: Bilkent WP3 deals with optical characterization and testing of photonic metamaterials. Leader: KIT WP4 deals with the dissemination of the photonic metamaterials results. Leader: Imperial WP5 deals with project management. Leader: FORTH

The objectives or tasks of the three work packages for the reporting period are the following:

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Objective: T1.1 Design of 3D connected PMMs and the extraction of the effective parameters and n.

Objective: T1.2 Software and method development to model 3D chiral metallic nanostructures.

Objective: T1.3 Self-consistent calculations of incorporating gain and non-linearity in PMMs. Reduction of losses.

Objective: T1.4 Blueprints for thin-film isolators, for electro-optic modulators and optical switching.

Objective: T2.1 Optimization of chemical-vapor-deposition (CVD) apparatus for metal coating of 3D templates from the inside.

Objective: T2.2 Conversion of theoretical blueprints from WP1 into 3D polymer structures that can actually be made via direct laser writing and CVD coating. Test of the designs in larger structures, operating at GHz range.

Objective: T2.3 Optimization of successive electron-beam lithography, electron-beam evaporation, and planarization processes specifically for the novel materials and substrates involved.

Objective: T3.2 Linear optical characterization of all PMMs made in WP2 and parameter retrieval.

Objective: T3.3 Experiments on frequency conversion from tailored structures designed in WP1 and fabricated in WP2).

Objective: T3.4 Luminescence experiments on emitters embedded in or in the vicinity of PMMs under low (modified spontaneous emission) and high (gain) optical pumping

2. Work progress and achievements during the periodWe have all the pdf files of our published and submitted papers in our web site (http://esperia.iesl.forth.gr/~ppm/PHOME/) and one can find all the details of these results.

During the second year (June 1, 2009 to May 31, 2010) we have done an excellent job in accomplishing all the objectives for the reporting period (June 1, 2009 to May 31, 2010). In summary we describe what we have accomplished in the following three WPs:

Theory and Simulation

1. Development of the retrieval procedure for chiral metamaterials to extract the effective parameters ( and n) with and without substrate.

2. Find new designs for planar and non-planar chiral metamaterials that give an alternative root for negative index of refraction, and give strong optical activity.

3. We have demonstrated for the first time, theoretically and numerically, that the Casimir force can be repulsive by using chiral metamaterials.

4. Losses in metamaterials render the applications of such exotic materials less practical unless an efficient way of reducing them is found. We present two different techniques to reduce ohmic losses at both lower and higher frequencies, based on geometric tailoring of the individual magnetic constituents. We show that an increased radius of curvature, in general, leads to the least losses in metamaterials. Particularly at higher THz frequencies, bulky structures outperform the planar structures.

5. We have developed a self-consistent method to treat active materials in dispersive media as metamaterials. This method can help understand if introducing gain materials in metamaterials can reduce the losses. We are working to implement this method to work for 3D structures.

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6. We have also presented new bulk designs that possess negative index of refraction at telecom frequencies and are easy to fabricate with direct laser writing, which is the most promising technique for the fabrication of truly 3D large scale optical metamaterials.

7. Using transformation optics, various plasmonic structures have been designed and studied analytically, whereas, until now, only the numerical tool was available for the study of such plasmonic devices. These nanostructures exhibit considerable nanofocusing capabilities: our theory predicts a field enhancement that can go beyond a factor of 104 over a broadband spectrum.

8. Radiation losses have been investigated both numerically and analytically in these devices. A good robustness relative to radiation losses has been predicted for structure dimension up to 400 nm. Nanostructures like a cylinder with a crescent-shaped cross-section or kissing cylinders are powerful light harvesting devices over a broadband spectrum, both in the visible and near infrared spectra.

Fabrication

1. A negative index of refraction due to three-dimensional chirality is demonstrated for a bilayered metamaterial based on pairs of mutually twisted planar metal patterns in parallel planes, which also shows negative electric and magnetic responses and exceptionally strong optical activity and circular dichroism.

2. Following our recent theoretical suggestion and microwave experiments, the UniKarl group has fabricated photonic metamaterials composed of pairs of twisted gold crosses and 4-U’s structures using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric.

3. Demonstration of a nonlinear photonic metamaterial by adding a nonlinear material (GaAs) to a split-ring-resonator array.

4. Fabricate structures that will be used for dynamic response of metamaterials at THz regime. They produce blueshift tenability and broadband simulation.

5. Direct laser writing (DLW) can be viewed as the three-dimensional analogue of electron-beam lithography. Fabrication of polymer structures by this approach is standard. In fact, we are using a commercial instrument from Nanoscribe GmbH (a collaboration with Carl Zeiss) that has emerged out of previous Karlsruhe work. Infilling or coating of such polymer structures with metals is not standard at all. We have pursued chemical-vapor deposition of silver and silver shadow evaporation. We have fabricated 2D metamaterials structures.

6. First realization of a three-dimensional gold-helix photonic metamaterial via direct laser writing into a positive-tone photoresist and subsequent infilling with gold via electroplating.

7. Finally, reaching beyond the original goals of PHOME first 3D invisibility cloaking structures have been realized – another striking demonstration of the future possibilities of our direct laser writing approach for making 3D metamaterials at optical frequencies.

Measurements

1. Free space transmission measurements of 1D and 2D chiral structures, at GHz frequencies, discovery of strong optical activity and negative refraction.

2. We have fabricated twisted-cross photonic metamaterials that exhibit strong and pure optical activity in a fairly large spectra range around 1.3 micron wavelength. In addition, we have used a different design (4-U’s) and exhibit strong activity at 3 micron wavelength.

3. Transmission properties of the bilayered form of the metamaterial for left-handed (LCP) and right-handed (RCP) circular polarizations. The structure shows exceptionally strong circular dichroism and strong rotation angle. Pure optical activity, i.e., polarization azimuth rotation

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without any change of ellipticity, is achieved between resonances, where the absolute rotation is about 800° per wavelength (6 GHz) and about 400° per wavelength (105 THz) for 4-U’s and about 60° per wavelength (220 THz) for crosee wires..

4. We have fabricated many split-ring resonator (SRR) structures on crystalline GaAs semiconductor substrates. We find strong coupling between the electromagnetic near-fields of the split rings and the underlying GaAs substrate, resulting in measured second-harmonic generation (SHG) that is about 25 times stronger than that we have previously found for split-ring-resonator arrays on glass substrate.

5. Such strong interaction between the SRRs and the underlying semiconductor is also crucial for compensating metamaterial losses by introducing gain. In our corresponding design studies, we have considered SRR on top of a thin gain layer. We using electron-beam lithography have also fabricated many corresponding structures. Various gain layers are available to us from cooperation partner, i.e., single quantum wells, three quantum wells, layers of quantum dots, or thin bulk films. A dedicated low-temperature femtosecond pump/probe experiment has been assembled. In this setup, pulses centered around 800-nm wavelength derived from a Ti:sapphire laser are used as the optical pump. Average powers around 100 mW focused to spots on the sample with diameters around 20-30 µm enable extremely strong pumping conditions, for which quantum well (QW) gain is expected. Fortunately, under these intense, essentially continuous-wave, pumping conditions, no sample deterioration has been observed. The probe pulses are derived from an optical parametric oscillator (OPO) that is tunable at around 1500-nm wavelength. The setup allows for detecting pump-induced changes in transmittance. The samples are cooled in a He-flow cryostat to increase the anticipated material gain. However, under conditions of intense pumping and at low temperatures, we have so far not found any “SPASING” action, which would be a clear-cut proof of complete compensation of metamaterial losses by the gain.

6. THz time-domain spectroscopy is used to probe the electromagnetic properties of metamaterials, that were fabricated within the PHOME, which are dynamically photo excited, using synchronized femtosecond near-infrared laser pulses. Blushift tunability of the metamaterials and a broadband phase tenability at about 45°. These results cab be used as a switching effect at THz frequencies.

7. We have fabricated and demonstrated metamaterials based enhanced transmission through sub-wavelength apertures.

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WP1: Theory and Modeling

A summary of progress towards objectives and details for each task

Work package 1 (WP1) is devoted to new design concepts and their simulations; these designs shall lead, among other goals, to optimized low-loss, broad bandwidth PMMs to be fabricated in WP2 and characterized in WP3. Development of new software and methods to model 3D chiral metamaterials will be also part of the WP1 efforts. In addition, we will also develop a self-consistent theory of incorporating gain or nonlinearity in PMMs. We have developed the 2D code for incorporating gain in metamaterials. We are working to implement the 3D code, which needs a lot of computer memory. Furthermore, blueprints for 3D metamaterials have been developed that acknowledge the conceptual boundary conditions of the novel corresponding fabrication approaches pursued in WP2. We have addressed all the four tasks T1.1 (Design of 3D connected PMMs and the extraction of the effective parameters ( and n), T1.2 (Software and method development to model 3D chiral metallic nanostructures), T1.3 (Self-consistent calculations of incorporating gain and non-linearity in PMMs. Reduction of losses), and T1.4 (Blueprints for thin-film isolators, for electro-optic modulators and optical switching) and we have substantial progress in the second year. We have followed the traditional way to reduce losses by eliminating the sharp corners, and also by geometric tailoring we found ways to reduce the losses. In addition, our Imperial partners have pursue another way to use transformation optics to design and study analytically novel plasmonic metamaterials structures showing nanofocusing abilities, (for details see the report written by our Imperial partners shown below).

Highlight clearly significant results

Negative refractive index response of weakly and strongly coupled fishnet metamaterials. The losses can be reduced and the figure of merit can increase. (PRB 2009, ref. 18).

Design of compact planar far-field superlens based on anisotropic left-handed metamaterials (PRB 2009, ref. 16).

First theoretically and numerically demonstration of the Casimir force is repulsive by using chiral metamaterials (PRL 2009, ref. 21).

First self-consistent calculation of 2D metamaterials with gain (PRB 2009, ref. 19). Design of planar and non-planar chiral metmaterials that give negative n and strong optical

activity (Opt. Lett. 2009, ref. 3, Opt. Lett. 2010, ref. 11, APL 2009, ref. 12, J. Opt. A 2009, ref. 14, Opt. Expr. 2009, ref. 15, Opt. Expr. 2010, ref. 35 & APL submitted).

Design of intra-connected 3D isotropic bulk negative index photonic metamaterial (Opt. Express 2009 ref. 23).

Reducing losses in metamaterials by geometric tailoring (PRB, 2009, ref. 20). Taking advantage of the analogy between negative refraction and phase conjugation,

lossless superlens schemes has been proposed and try to figure out if this can be demonstrated experimentally (JOSA B 2010 ref. 40).

Based on conformal transformation, a general strategy is proposed to design plasmonic capable of an efficient harvesting of light over a broadband spectrum (Nano Letters, in press, ref. 41).

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Future plans

Following our proposal and the above status report, we will continue to pursue the goals of this project in a straightforward manner. In particular, our next steps regarding the theory/modeling effort:

Design new chiral structures and optimize them that will give negative n and strong optical activity. These new chiral designs, with strong chirality can be used to obtain repulsive Casimir force.

Plan to study the coupling effect between two adjacent layers of coupled chiral layers. We need to study the weakly coupled and strongly coupled chiral layers. Are the retrieved effective parameters for one layered chiral structure is the same for many layers?

Design new interconnected structures that will give negative and negative n at GHz, THz and micron frequencies, which can be fabricated by traditional methods at GHz frequencies, and direct laser writing at THz and micron frequencies.

We plan to extend the gain code in 3D so we can be able to treat realistic cases of metamaterials by introducing gain material so we will be able reduce the losses in metamaterials. This code can help us to see if we will be able to get lasing through surface plasmons, which is called “SPASING.”

The physics of the interaction between plasmonic nanoparticles has been revisited with transformation optics. Novel physical insights have been provided regards the resonant behavior of these nanostructures and the nanofocusing properties that can be expected with nanoparticle dimers. We plan to use 2D wedge-like structures, tapered wave guides, open nanocrescents or overlapping cylinders than can be able to exhibit a singularity, which may give rise to a divergence of the electric field, even in presence of dissipation losses. This singular behavior had not been pointed out in the past and can be of great interest for single molecule detection.

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WP2: Fabrication of photonic metamaterials

A summary of progress towards objectives and details for each task

Work package 2 (WP2) is devoted to a systematic study of materials and processing methods to optimize the quality of micro- and nanofabricated PMMs. Furthermore; novel fabrication approaches shall be explored for 3D structures. The latter idea is very risky, but it is worth pursuing, especially in the spirit of the FET program, which supports exploitation of ideas that can open new possibilities and set new trends for feature research. As PMMs are scaled to higher frequencies, the quality of materials and fabrication becomes of increasing importance. Because PMMs are based on resonant micro and nanostructured conductors, fabrication tolerance and surface quality are crucial. Our team brings extraordinary fabrication capabilities, with access to nearly all state-of-the-art fabrication facilities, including electron- and focused-ion-beam (FIB) lithography, as well as direct laser writing for true 3D structures. During the first two years, we have performed a careful study of the various figures-of-merit of NIM prototypes as a function of fabrication conditions, including material deposition conditions, annealing and surface smoothness, and quality as characterized by atomic-force microscopy. We have addressed the three tasks of WP2, T2.1 (Optimization of chemical-vapor-deposition (CVD) apparatus for metal coating of 3D templates from the inside), T2.2 (Conversion of theoretical blueprints from WP1 into 3D polymer structures that can actually be made via direct laser writing and CVD coating. Test of the designs in larger structures, operating at GHz range), and T2.3 (Optimization of successive electron-beam lithography, electron-beam evaporation, and planarization processes specifically for the novel materials and substrates involved). In detail, as proposed, we have pursued two alternative and complementary fabrication approaches for three-dimensional (3D), i.e., non-planar, photonic metamaterials: (i) Direct laser writing and (ii) stacking of layers made via electron-beam lithography. While we have considered the novel approach (i) as very risky at the time of the proposal, it has delivered several results already and even unexpected variations of this approach are emerging from KIT.

Highlight clearly significant results

First realization of a three-dimensional gold-helix photonic metamaterial as broadband circular polarizer (Science 2009, ref. 2 & Opt. Expr. 2009, ref. 8).

First demonstration of a photonic chiral metamaterial made via 3D direct laser writing (Opt. Lett. 2010, ref.9).

First demonstration of 3D invibility cloak at optical wavelengths made via 3D direct laser writing (Science 2010, ref. 10)

Fabrications of planar chiral metamaterials that give negative n and strong optical activity at GHz frequencies (Opt. Expr. 2010, ref. 35 & APL submitted, ref. 39).

First fabrication of non-planar chiral metamaterial that give negative n at GHz frequencies (APL 2009, ref. 12 & J. Opt. A 2009, ref. 14).

Fabrication of twisted-cross photonic metamaterials at 1.5 micron with strong optical activity (Opt. Lett. 2009, ref. 3).

Fabrication of 4-U’s photonic metamaterials at 3 micron with strong optical activity (Opt. Lett. 2010, ref. 11).

Dynamic response of metamaterials in the THz regime: Blue shift tunability and broadband phase modulation (APL. 2010, ref. 22).

Demonstration of a nonlinear photonic metamaterial by adding a nonlinear material (GaAs) to a split-ring-resonator array (Opt. Lett. 2009, ref. 1).

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Metamaterials based enhanced transmission through sub-wavelength apertures (J. Opt. A 2009, ref. 26, APL 2009, ref. 28 & Opt. Expr. 2010, ref. 36).

Future plans

Following our proposal and the above status report, we will continue to pursue the goals of this project in a straightforward manner. In particular, our next steps regarding the above major avenues are:

Fabrication of chiral metamaterials for GHz, THz and micron wavelengths. Realize the negative-index metamaterial structure developed by the FORTH group via DLW

and chemical-vapor deposition (CVD). Technologically, we have to succeed in performing a lift-off process of the undesired metal film deposited at the glass substrate surface (CVD).

Publish our results on DLW and gold electroplating and further optimize and explore these appealing three-dimensional gold-helix metamaterials regarding bandwidth. Possibly, these structures also allow for a negative phase velocity of light.

Fabricate new structures that will be used for switching and dual-band switching at THz frequencies. In addition, we plan to fabricate tunable chiral metamaterial.

Further explore the effects of SRR interactions in passive systems in view of the lasing SPASER.

Explore other geometries aiming at demonstrating the lasing SPASER for photonic metamaterials with much (!) lower losses than currently available. This aspect is extremely risky.

Fabricate new electromagnetic induced transparency structures that will be used to reduce the speed of light dramatically.

Explore tuning and modulation of optical metamaterials via modulation of the metal properties in electrolytic environments in analogy to field-effect-transistor based concepts at THz frequencies. This concept would be applicable to any type metamaterial (e.g., negative-index, chiral) or plasmonic structure with large surface-to-volume ratio.

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WP3: Optical characterization and testing

A summary of progress towards objectives and details for each task

Work package 3 (WP3) is devoted to the characterization of the metamaterial structures made in WP2. The fabrication in WP2 is obviously intimately interwoven with the optical characterization and testing in WP3. Thus below, the significant results are the same as in WP2. This requires innovative approaches regarding the retrieval of optical constants from experimentally accessible parameters. The experiments include THz time-domain spectroscopy, optical transmittance and reflectance spectroscopy, laser based interferometry, near-field optical spectroscopy, as well as nonlinear optical spectroscopy. These measurements will be accompanied by thorough theoretical analysis and modeling emerging from WP1. With the combined efforts of Work packages 1-3, photonic metamaterials could make the step from sub-wavelength thickness films towards truly 3D materials. If this risky enterprise is successful, the step to ICT relevant devices and demonstrators is small. Examples are “poor man’s” optical isolators, optical switching, and electro-optic modulators. During the first two years, we have address all the tasks of WP3, T3.1 (Optical characterization of all PMMs made in WP2), T3.2 (Linear optical characterization of all PMMs made in WP2 and parameter retrieval), T3.3 (Experiments on frequency conversion from tailored structures designed in WP1 and fabricated in WP2), T3.4 (Luminescence experiments on emitters embedded in or in the vicinity of PMMs under low (modified spontaneous emission) and high (gain) optical pumping).

Much of the optical metamaterial characterization performed by KIT in this project is not standard at all. This comprises the following set-ups:

Quantitative optical spectroscopy on individual metamaterial elements (“photonic atoms”). We have put much effort into further optimizing data quality as well as into reducing measurement times by replacing the pervious mechanical translation stages by piezoelelectric actuators along all thee spatial axes. This step has allowed extensive studies on “photonic molecules” of SRR (made via electron-beam lithography) in which we have systematically investigated the effects of SRR distance and orientation. As outlined above, this work is important for avoiding break-up effects in metamaterials incorporating optical gain.

Optical spectroscopy with circularly polarized incident light in the visible and near-infrared. Our corresponding home-built set-up has been further improved, now also allowing for analysis of the state of polarization emerging from the metamaterial sample.

Optical spectroscopy with circularly polarized incident light in the mid-infrared. As described in the proposal, we are operating two commercial Fourier-transform microscopy-spectrometers allowing for spectroscopy on small samples up to wavelengths of about 10 µm. These instruments did not allow for circular polarization of the incident light at all – which, however, is crucial for characterizing three-dimensional chiral metamaterial structures. Thus, we have custom modified these instruments: A home-made compact holder encompasses a linear CaF2 “High Extinction Ratio” holographic polarizer and a super-achromatic quarter-wave plate that can be rotated from the outside of the microscope. The custom-made MgF2 based super-achromatic quarter-wave plate (Bernhard Halle Nachfl.) has a phase error below only ± 14 % in the entire spectral range from 2.5 to 7.0 µm wavelength of light. This modification allows for conveniently adjusting left and right-handed circular polarization of the incident light. Furthermore, we have modified the reflective ×36 Cassegrain optics with NA=0.5 by introducing a small diaphragm such that

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the full opening angle of the light incident onto the sample is reduced to about 5 degrees. By tilting the sample we achieve actual normal incidence of light onto the sample.

A dedicated low-temperature femtosecond pump/probe experiment has been assembled. In this setup, pulses centred around 800-nm wavelength derived from a Ti:sapphire laser are used as the optical pump. Average powers around 100 mW focused to spots on the sample with diameters around 20-30 µm enable extremely strong pumping conditions, for which quantum well (QW) gain is expected. Fortunately, under these intense, essentially continuous-wave, pumping conditions, no sample deterioration has been observed. The probe pulses are derived from an optical parametric oscillator (OPO) that is tunable at around 1500-nm wavelength. The setup allows for detecting pump-induced changes in transmittance. The samples are cooled in a He-flow cryostat to increase the anticipated material gain. This set up will be used to see if we can compensate the losses by gain material.

Highlight clearly significant results

First realization of a three-dimensional gold-helix photonic metamaterial as broadband circular polarizer (Science 2009, ref. 2 & Opt. Expr. 2009, ref. 8).

First demonstration of a photonic chiral metamaterial made via 3D direct laser writing (Opt. Lett. 2010, ref.9).

First demonstration of 3D invibility cloak at optical wavelengths made via 3D direct laser writing (Science 2010, ref. 10)

Fabrications of planar chiral metamaterials that give negative n and strong optical activity at GHz frequencies (Opt. Expr. 2010, ref. 35 & APL submitted, ref. 39).

First fabrication of non-planar chiral metamaterial that give negative n at GHz frequencies (APL 2009, ref. 12 & J. Opt. A 2009, ref. 14).

Fabrication of twisted-cross photonic metamaterials at 1.5 micron with strong optical activity (Opt. Lett. 2009, ref. 3).

Fabrication of 4-U’s photonic metamaterials at 3 micron with strong optical activity (Opt. Lett. 2010, ref. 11).

Dynamic response of metamaterials in the THz regime: Blue shift tunability and broadband phase modulation (APL. 2010, ref. 22).

Demonstration of a nonlinear photonic metamaterial by adding a nonlinear material (GaAs) to a split-ring-resonator array (Opt. Lett. 2009, ref. 1).

Metamaterials based enhanced transmission through sub-wavelength apertures (J. Opt. A 2009, ref. 26, APL 2009, ref. 28 & Opt. Expr. 2010, ref. 36).

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WP4: Dissemination of the photonic metamaterials results

In the current reporting period we had a large number of publications and invited talks at conferences and institutions, where we advertised the PHOME results. Below we mention some steps, planned or done, towards dissemination and use of the PHOME results..

We have created a web page where we plan to put our articles on PMMs and our main results. This page is linked to the CORDIS sites, it gives links to the main groups working on the area of metamaterials and it will be connected also to the main metamaterial related web pages in the near future.

We present and we will continue to present the PHOME results through publications, colloquia, and participations to conferences and workshops.

We have organized sessions devoted to PMMs at international conferences (ETOPIM 8, Rethymnon, Crete, Greece, June 2009; SPIE 2009, San Diego, USA, August 2009; Metamaterials Congress Conference, London, UK September 2009; Medi-Nano 2, Athens, Greece, October 2009; 2nd International Workshop on Theoretical and Computational Nanophotonics (TaCoNa-Photonics), Bad Honnef, Germany, December 2009; MRS Fall Meeting, Boston, USA December 2009; 40th Winter Colloquium of Quantum Electronics, Snowbird, USA, January 2010; META’10, Egypt, Cairo, February 2010), where PHOME results will be advertised.

We have organized a school devoted to “Fabrication and optical properties of nanostructured metamaterials”, Rethymnon, Crete, June 2009, where many young researchers had the chance to familiarize themselves with the field of photonic metamaterials.

The experimental group of Karlsruhe is in discussion with industries about potential applications of PMMs as optical isolators.

We plan to send any information (high level publication, appearances of FET projects etc.) to the DG Information Society

Below we list publications and the invited talks and seminars on photonic metamaterials, which took place during the current reporting period. The publications are listed also at the project webpage, at http://esperia.iesl.forth.gr/~ppm/PHOME/

Puclications:

1. F.B.P. Niesler, N. Feth, S. Linden, J. Niegemann, J. Gieseler, K. Busch, and M. Wegener, “Second-harmonic generation from split-ring resonators on a GaAs substrate,” Opt. Lett. 34, 1997 (2009).

2. J.K. Gansel, M. Thiel, M.S. Rill, M. Decker, K. Bade, V. Saile, G. von Freymann, S. Linden, and M. Wegener, “Gold helix photonic metamaterial as broadband circular polarizer,” Science 325, 1513 (2009).

3. M. Decker, M. Ruther, C. Kriegler, J. Zhou, C.M. Soukoulis, S. Linden, and M. Wegener, “Strong optical activity from twisted-cross photonic metamaterials,” Opt. Lett. 34, 2501 (2009).

4. M. Decker, S. Burger, S. Linden, and M. Wegener, “Magnetization waves in split-ring-resonator arrays: Evidence for retardation effects,” Phys. Rev. B 80, 193102 (2009).

5. J.C. Halimeh, T. Ergin, J. Mueller, N. Stenger, and M. Wegener, “Photorealistic images of carpet cloaks,” Opt. Express 17, 19328 (2009).

6. C.E. Kriegler, M.S. Rill, S. Linden, and M. Wegener, “Bianisotropic photonic metamaterials,” IEEE J. Sel. Top. Quant. 16, 367 (2010).

7. N. Feth, M. König, M. Husnik, K. Stannigel, J. Niegemann, K. Busch, M. Wegener, and S. Linden, “Pairwise electromagnetic interaction of split-ring resonators: The role of separation and relative orientation,” Opt. Express 18, 6545 (2010).

8. J.K. Gansel, M. Wegener, S. Burger, and S. Linden, “Gold helix photonic metamaterials: A numerical parameter study,” Opt. Express 18, 1059 (2010)

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9. M. Thiel, H. Fischer, G. von Freymann, and M. Wegener, “Three-dimensional chiral photonic superlattices,” Opt. Lett. 35, 166 (2010).

10. T. Ergin, N. Stenger, P. Brenner, J.B. Pendry, and M. Wegener, “Three-Dimensional Invisibility Cloak at Optical Wavelengths,” Science 328, 337 (2010).

11. M. Decker, R. Zhao, C.M. Soukoulis, S. Linden, and M. Wegener, “Twisted split-ring-resonator photonic metamaterial with huge optical activity”, Opt. Lett. 35 (10), 1593 (2010).

12. B. Wang, J. Zhou, M. Kafesaki, Th. Koschny and C. M. Soukoulis, “Nonplanar Chiral Metamaterials with Negative Index”, App. Phys. Lett. 94, 151112 (2009).

13. N. H. Shen, G. Kenanakis, M. Kafesaki, N. Katsarakis, E. N. Economou, and C. M.Soukoulis, “Parametric investigation and analysis of fishnet metamaterials in the microwave regime”, J. Opt. Soc. Am B 26, B61 (2009).

14. B. N. Wang, J. F. Zhou, Th. Koschny, M. Kafesaki, and C. M.Soukoulis, “Chiral metamaterials: simulations and experiments”, J. Opt. A: Pure and Appl. Opt. 11, 114003 (2009).

15. J. Dong, J. Zhou, Th. Koschny, and C. M. Soukoulis, “Bi-layer cross chiral structure with strong optical activity and negative refractive index,” Optics Express 17, 14173 (2009).

16. N. H. Shen, S. Foteinopoulou, M. Kafesaki, Th. Koschny, E. Ozbay, E. N. Economou, and C. M. Soukoulis, “Compact planar far-field superlens based on anisotropic left-handed metamaterials”, Phys. Rev. B 80, 115123 (2009).

17. E. N. Economou, M. Kafesaki, C. M. Soukoulis, and Th. Koschny, “The fourth quadrant in the epsilon-mu plane: A new frontier in Optics”, J. Comp. Theor. Nanoscience 6, 1827 (2009).

18. J. Zhou, Th. Koschny M. Kafesaki and C. M. Soukoulis, “Negative refractive index response of weakly and strongly coupled optical metamaterials”, Phys. Rev. B 80, 035109 (2009).

19. A. Fang, Th. Koschny, M. Wegener and C. M. Soukoulis, “Self-consistent calculation of metamaterials with gain”, Phys. Rev. B 79 241104(R) (2009).

20. D. Ö. Güney, Th. Koschny, and C. M. Soukoulis, “Reducing Ohmic losses in metamaterials by geometric tailoring,” Phys. Rev. B 80, 125129 (2009).

21. R. Zhao, J. Zhou, Th. Koschny, E. N. Economou and C. M. Soukoulis, “Repulsive Casimir force in chiral memamaterials,” Phys. Rev. Lett. 103, 103602 (2009).

22. J.M. Manceau, N.-H. Shen, M. Kafesaki, C. M. Soukoulis, and S. Tzortzakis, “Dynamic response of metamaterials in the terahertz regime: Blue shift tunability and broadband phase modulation”, Appl. Phys. Lett. 96, 021111 (2010).

23. D. Ö. Güney, Th. Koschny, and C. M. Soukoulis, “Intra-connected 3D isotropic bulk negative index photonic metamaterial”, Opt. Exp. 18, 12352 (2010).

24. R. S. Penciu, M. Kafesaki, Th. Koschny, E.N. Economou, and C.M. Soukoulis, “Magnetic response of nanoscale left-handed metamaterials”, Phys. Rev. B (accepted).

25. A.E Serebryannikov and E. Ozbay, “Multifrequency invisibility and masking of cylindrical dielectric objects using double-positive and double-negative metamaterials,” J. Opt. A: Pure Appl. Opt. 11, 114020 (2009).

26. F. Bilotti, L. Scorrano, E. Ozbay and L. Vegni, “Enhanced transmission through a sub-wavelength aperture: resonant approaches employing metamaterials,” J. Opt. A: Pure Appl. Opt. 11, 114029 (2009).

27. P.V. Usik, A.E. Serebryannikov, and E. Ozbay, “Spatial and spatial-frequency filtering using one-dimensional graded-index lattices with defects,” Opt. Commun. 282, 4490 (2009).

28. A.O. Cakmak, K. Aydin, E. Colak, Z. Li, F. Bilotti, L. Vegni and E. Ozbay, “Enhanced transmission through a subwavelength aperture using metamaterials,” Appl. Phys. Lett. 95 052103 (2009).

29. A.E Serebryannikov and E. Ozbay, “Unidirectional transmission in non-symmetric gratings containing metallic layers,” Opt. Exp. 17, 13335 (2009).

30. K.B. Alici and E. Ozbay, “Oblique response of a split-ring-resonator-based left-handed metamaterial slab,” Opt. Lett. 34, 2294 (2009).

31. K.B. Alici and E. Ozbay, “Direct observation of negative refraction at the millimeter-wave regime by using a flat composite metamaterial,” J. Opt. Soc. Am. B 26, 1668 (2009).

32. A.E. Serebryannikov, P.V. Usik and E. Ozbay, “Non-ideal cloaking based on Fabry-Perot resonances in single-layer high-index dielectric shells,” Opt. Exp. 17 [19] 16869 (2009).

33. E. Colak, H. Caglayan, A.O. Cakmak, A.D. Villa, F. Capolino and E. Ozbay, “Frequency dependent steering with backward leaky waves via photonic crystal interface layer,” Opt. Exp. 17, 9879 (2009).

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34. A.O. Cakmak, E. Colak, H. Caglayan, H. Kurt and E. Ozbay, “High efficiency of graded index photonic crystal as an input coupler,” J. Appl. Phys. 105, 103708 (2009).

35. Z. Li, H. Caglayan, E. Colak, J. Zhou, C. M. Soukoulis and E. Ozbay, “Coupling effect between two adjacent chiral structure layers,” Opt. Exp. 18, 5375 (2010).

36. D. Ates, A.O. Cakmak, E. Colak, R. Zhao, C. M. Soukoulis, and E. Ozbay, “Transmission enhancement through deep subwavelength apertures using connected SRRs,” Opt. Exp. 18, 3952 (2010).

37. T. F. Gündogdu, K. Güven, M. Gökkavas, C. M. Soukoulis and E. Özbay, “A Planar Metamaterial With Dual-Band Double-Negative Response at EHF,” IEEE J. Sel. Top. Quantum Electron. 166, 376 (2010).

38. K. B. Alici. and E. Ozbay, “Theoretical Study and Experimental Realization of a Low-Loss Metamaterial Operating at the Millimeter-Wave Regime: Demonstrations of Flat- and Prism-Shaped Samples,” IEEE J. Sel. Top. Quantum Electron. 166, 386 (2010).

39. Z. Li, R. Zhao, Th. Koschny, M. Kafesaki, E. Colak, H. Caglayan, E. Ozbay and C. M. Soukoulis, “Chiral metamaterials with negative refractive index based on Four-U-SRRs resonators,” Appl. Phys. Lett. (submitted).

40. A. Aubry and J. B. Pendry, "Mimicking a negative refractive slab by combining two phase conjugators," J. Opt. Soc. Am. B 27, 72-84 (2010).

41. . Aubry, D. Y. Lei, A.I. Fernandez-Dominguez, Y. Sonnefraud, S. A. Maier and J. B. Pendry, "Plasmonic light harvesting devices over the whole visible spectrum," Nano Letters (submitted).

42. A. Aubry, D. Y. Lei, S. A. Maier and J. B. Pendry, "A broadband plasmonic device concentrating the energy at the nanoscale: The crescent-shaped cylinder," New J. Phys. (submitted).

43. D. Y. Lei, A. Aubry, S. A. Maier and J. B. Pendry, "A broadband plasmonic device concentrating the energy at the nanoscale: The kissing cylinders," Phys. Rev. B (submitted).

PHOME 213390 Page 17

Conference presentations (only Invited Talks listed here)

1. Kafesaki , ICMAT 2009: International Conference on Materials for Advanced Technologies 2009, Singapore, June 28 - July 3, 2009.

2. M. Kafesaki , Metamaterials Congress 2009, London, UK, August 30 - September 4, 2010.3. M. Kafesaki , 25th PanHellenic Conference on Solid State Physics and Materials Science, Thessaloniki,

Greece, September 20-23, 2010.4. M. Kafesaki , 2nd International Conference on Metamaterials, Photonic Crystals and Plasmonics

(Meta'10), Cairo, Egypt, January 22-25, 2010.5. M. Kafesaki , Workshop on "Metamaterials: Applications, Analysis and Modeling", Los Angeles, USA,

January 25-29, 2010.6. M. Kafesaki , SPIE conference “Photonics Europe: Matamaterials”, Brussels, Belgium, April 12-16,

2010.7. C. M. Soukoulis , International Conference on Electrical, Transport and Optical Properties of

Inhomogeneous Media (ETOPIM 8), Rethymon, Crete, Greece, June 7-12, 2009.8. C.M. Soukoulis , SPIE Optics and Photonics, San Diego, Ca, USA, August 2-6, 2009.9. C. M. Soukoulis , Third International Congress on Advanced Electromagnetic Materials in Microwaves

and Optics (Metamaterials 2009), London, UK, August 30-Sept 4, 2009.10. C. M. Soukoulis , International Commission for Optics Topical Meeting on “Emerging Trends and Novel

Materials in Photonics”, Delphi, Greece, October 7-9, 2009.11. C.M. Soukoulis , Plenary Talk, 2nd Mediterranean Conference on Nano-Photonics (Medi-Nano 2),

Athens, Greece, October 27-29, 2009.12. C. M. Soukoulis , Fall Meeting of the Materials Research Society, Boston, Massachusetts, November

2009.13. C. M. Soukoulis , Plenary Talk, Meta’10 2nd International Conference on Metamaterials, Photonic

Crystals and Plasmonics, Cairo Egypt, February 22-25, 2010.14. C. M. Soukoulis , International Workshop on Photonic Nanomaterials - PhoNa 2010, Jena, Germany,

March 24-26, 2010.15. M.S. Rill , C. Plet, M. Thiel, A. Frölich, I. Staude, M. Wegener, G. von Freymann, and S. Linden,

“Towards 3D Isotropic Photonic Metamaterials via Direct Laser Writing”, The 2nd European Topical Meeting on Nanophotonics and Metamaterials, Seefeld (Austria), January 5-8, 2009.

16. S. Linden , N. Feth, M. Husnik, M. Wegener, M. König, J. Niegemann, and K. Busch, “Spectroscopy of individual split-ring resonators”, The 2nd European Topical Meeting on Nanophotonics and Metamaterials, Seefeld (Austria), January 5-8, 2009.

17. M. Wegener , “Photonic Metamaterials: Recent Progress”, IEEE/LEOS Winter Topical Meeting on Nanophotonics, Innsbruck (Austria), January 12-14, 2009 .

18. M. Wegener and S. Linden, “Photonic Metamaterials: Recent Progress”, Annual Dutch Physics Meeting “Physics@FOM 2009”, Veldhoven (The Netherlands), January 20-21, 2009.

19. M. Wegener , “Photonic Metamaterials: Optics Starts Walking on Two Feet”, European Action COST Training School on “Nonlinear Nanophotonics”, Metz (France), March 23-25, 2009.

20. M. Wegener and S. Linden, “Photonic Metamaterials: Recent Progress”, PECS VIII – The 8th International Photonic & Electromagnetic Crystal Structures Meeting, Cockle Bay Warf, Sydney (Australia), April 5-9, 2009.

21. S. Linden, K. Busch, N. Feth, G. von Freymann, J. Gansel, H. Hein, M. Husnik, P.-J. Jakobs, M.F.G. Klein, M. König, N. Meinzer, J. Niegemann, C. Plet, M. Rill, C.M. Soukoulis, M. Thiel and M. Wegener, “Recent Progress on Photonic Metamaterials”, Spring Meeting of the Materials Research Society (MRS), San Francisco (U.S.A.), April 13-17, 2009.

22. M. Wegener , “Photonic Metamaterials: Quo Vadis?”, 8th International Conference on “Electrical, Transport and Optical Properties of Inhomogeneous Media (ETOPIM 8)”, Rethymnon, Crete (Greece), June 7-12, 2009.

23. M. Wegener , “Photonic Metamaterials: Recent Progress”, European Quantum Electronics Conference (EQEC) 2009, Munich (Germany), June 14-19, 2009.

24. M. Wegener and S. Linden, “Photonic Metamaterials: Recent Progress”, International Conference on “Surface Plasmon Photonics-4 (SPP4)”, Amsterdam (The Netherlands), June 21-26, 2009.

PHOME 213390 Page 18

25. M. Wegener , “Photonic Metamaterials: Magnetism Enters Photonics”, International Conference on Magnetism 2009 (ICM'09), Karlsruhe (Germany), July 26-31, 2009.

26. M. Wegener , “Photonic Metamaterials: Optics Starts Walking on Two Feet”, SPIE 2009 Optics and Photonics Meeting, San Diego (U.S.A.), August 2-6, 2009.

27. M. Wegener , “Photonic Metamaterials: Three-Dimensional Structures and Loss Compensation”, “Metal Nanostructures and Their Optical Properties VII”, SPIE 2009 Optics and Photonics Meeting, San Diego (U.S.A.), August 2-6, 2009

28. M. Wegener , M. Decker, and S. Linden, “Interaction Effects in Low-Symmetry Split-Ring Resonator Arrays”, “Metamaterials: Fundamentals and Applications II”, SPIE 2009 Optics and Photonics Meeting, San Diego (U.S.A.), August 2-6, 2009.

29. S. Linden, N. Feth, M. Husnik, M. König, J. Niegemann, K. Busch, and M. Wegener, “Spectroscopy of individual photonic atoms”, “Metamaterials: Fundamentals and Applications II”, SPIE 2009 Optics and Photonics Meeting, San Diego (U.S.A.), August 2-6, 2009.

30. M. Wegener , “Photonic Metamaterials: Optics Starts Walking on Two Feet”, Summer School “New Frontiers in Optical Technologies”, Tampere (Finland), August 10-14, 2009.

31. M. Wegener , “Photonic Metamaterials: Recent Progress”, Fall Meeting of the Material Research Society (MRS) of America, Boston (U.S.A.), November 30 - December 4, 2009.

32. M. Wegener , Plenary Talk, “Towards 3D photonic metamaterials”, 40th Winter Colloquium on the “Physics of Quantum Electronics”, Snowbird (U.S.A.), January 3-7, 2010.

33. J.K. Gansel, M. Thiel, M.S. Rill, M. Decker, K. Bade, V. Saile, G. von Freymann, S. Linden and M. Wegener, “Three-dimensional gold-helix photonic metamaterials made via two-photon direct laser writing”, International Conference Photonics West, “Synthesis and Photonics of Nanoscale Materials VII”, San Francisco (U.S.A.), January 25-28, 2010.

34. M. Wegener , Plenary Talk, “3D Chiral photonic crystals and metamaterials”, 2nd International Conference on “Metamaterials, Photonic Crystals and Plasmonics”, Cairo (Egypt), February 22-25, 2010.

35. M. Wegener , “Photonic Crystals and Metamaterials”, “19. Diskussionstagung Anorganisch-Technische Chemie”, DECHEMA House, Frankfurt (Germany), February 18-19, 2010.

36. M. Wegener , “3D Photonic Metamaterials Made by Direct Laser Writing”, March Meeting of the American Physical Society (APS), “Celebrating 50 Years of Lasers in Condensed Matter Physics: Surfaces, Imaging & Technology”, Portland (U.S.A.), March 15-19, 2010.

37. M. Wegener , Invited Tutorial, “Fabrication and characterization of chiral photonic metamaterials”, MRS Spring Meeting, San Francisco (U.S.A.), April 5-9, 2010.

38. M. Wegener , Invited Tutorial, “Photonic Metamaterials: Optics Starts Walking on Two Feet”, 15th European Conference on Integrated Optics (ECIO 10), Cambridge (United Kingdom), April 7-9, 2010.

39. S. Linden, J.K. Gansel, M. Decker, and M. Wegener, “Chiral metamaterials for optical frequencies”, SPIE Photonics Europe, Brussels (Belgium), April 12-16, 2010.

40. M. Wegener , “Photonic metamaterials go three-dimensional”, International Conference on Quantum Electronics and Laser Science (QELS), San Jose (U.S.A.), May 16-21, 2010.

41. M. Wegener , “3D Photonic Metamaterials Made by Direct Laser Writing” Plenary Talk, OSA Optics & Photonics Congress, Karlsruhe (Germany), June 21-24, 2010.

42. M. Wegener , “Bragg Gratings, Photosensitivity and Poling in Glass Waveguides”, OSA Optics & Photonics Congress, Karlsruhe (Germany), June 21-24, 2010.

43. J.B. Pendry , invited talk – ETOPIM8, June 2009.44. J.B. Pendry, invited talk – Erlangen, June 2010.45. J.B. Pendry , plenary talk – ICMAT Singapore, June 2009.46. J.B. Pendry , invited talk – ICMAT Singapore, June 2009.47. J.B. Pendry , presentation – DARPA kickoff Duke, July 2009.48. J.B. Pendry , plenary talk – London Metamaterials conference, Sept 2009.49. J.B. Pendry , plenary talk – ATOM by ATOM conf San Sebastian, Sept 2009.50. J.B. Pendry , invited talk – Maxwell Symposium London, Oct 2009.51. J.B. Pendry , invited talk – Hong Kong City university, Oct 2009.52. J.B. Pendry , plenary – CMMP10 Warwick UK, Dec 2009.53. J.B. Pendry , plenary – PQE Snowbird, Jan 2010.54. J.B. Pendry , Hamilton lecture – Princeton, April 2010.

PHOME 213390 Page 19

55. J.B. Pendry , talk – Triservices metamaterials review, Norfolk VA, May 2010.56. E. Ozbay, Plenary Talk, “The Magical World of Metamaterials”, IEEE Photonics Society Annual

Meeting 2009, Antalya, TURKEY, October 4-8 2009. 57. E. Ozbay , “The Magical World of Metamaterials”, 2nd Mediterranean Conference on Nano-Photonics

MediNano-2, Athens, Greece, October 26-27, 2009. 58. E. Ozbay , “The Magical World of Metamaterials”, Metamaterials Congress 2009, London, September 1-

4 2009. 59. Ekmel Ozbay , “Photonic Metamaterials” Inauguration Symposium, Max Planck Institute for the Science

of Light, Erlangen, Germany, 8-9 July 2009. 60. Ekmel Ozbay , “Nanophotonics and its Applications to Radiology” ESPR 2009, European Society of

Pediatric Radiology, Istanbul, June 1-4 2009.61. Bayram Butun , and Ekmel Ozbay, “GaN Based Nanophotonics Light Sources”, Invited Talk, European

Action COST Winter School on “Novel Gain Materials and Devices Based on III-V-N Compounds”, Istanbul, TURKEY, April 12, 2010.

62. Kaan Guven , Elena Saenz, Ramon Gonzalo, Sergei Tretyakov, and Ekmel Ozbay, “Metamaterial-based cloaking with sparse distribution of spiral resonators,” SPIE Photonics Europe, Strasbourg, France April 12-16, 2010.

63. E. Ozbay , “The Magical World of Metamaterials”, 2010 MRS Spring Meeting, San Francisco, USA, April 5-9, 2010.

64. E. Ozbay , “Nanophotonics and Metamaterials for Security Applications ”, Global Terrorism and International Cooperation-III, Ankara, TURKEY, March 15-16, 2010.

65. E. Ozbay , “The Magical World of Optical Metamaterials”, 16th Seminar on Electron and Ion Beam Lithography for Applications, Dortmund, GERMANY, February 22-24, 2010.

Talks/Seminars

M. Wegener

“Photonic Metamaterials: Optics Starts Walking on Two Feet”, Colloquium, University Vienna, March 2009.“Photonische Metamaterialien”, NanoMat Szene, Karlsruhe, March 2009.“Photonic Metamaterials: Optics Starts Walking on Two Feet”, Colloquium, University Dresden, April 2009.“Photonic Metamaterials: Optics Starts Walking on Two Feet”, Colloquium, University Mainz, May 2009.“Photonic Metamaterials: Optics Starts Walking on Two Feet”, Colloquium, University Chemnitz, May 2009.“Maßgeschneiderte nanostrukturierte Materialien für die Optik & Photonik”, KIT im Rathaus, Karlsruhe, June 2009.“Photonic Metamaterials: Optics Starts Walking on Two Feet”, Colloquium, University Dortmund, June 2009.“Photonic Metamaterials: Optics Starts Walking on Two Feet”, Workshop of IMTEK and FZK/KIT, Karlsruhe, September 2009.“Photonische Metamaterialien”, Colloquium, University Aachen, December 2009.“Metamaterialien und Transformationsoptik”, Colloquium of PTB, Braunschweig, March 2010.“3D Direct-Laser-Writing Lithography for Nanophotonics and Biology”, Optoelectronics Research Centre (ORC), Southampton, March 2010.“Metamaterials and Transformation Optics: Experiment Chasing After Theory”, Colloquium at Imperial College, London, April 2010.“Metamaterialien und Transformationsoptik”, Colloquium, University Göttingen, May 2010.

J. B. Pendry

ETH Zurich, Colloquium, September 2009.Discovery Park, Distinguished Lecture – Purdue, Discovery Park Distinguished Lecture, November 2009.Purdue, Public lecture, November 2009.

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Twente, December 2009.Berkeley, Seminar, January 2010.J.B. Pendry, public lecture – Nantes, France, February 2010.Fresnel Inst France, March 2010.Exeter, March 2010.HKUST, IAS distinguished lecture, March 2010.Princeton, Seminar, April 2010.Duke, Seminar, May 2010.NSU, Public lecture, May 2010.

C. M. Soukoulis

Institute of Atomic and Molecular Physics (AMOLF), FOM, Amsterdam, Netherlands, June 2009Department of Physics, University of Minnesota, Minneapolis, USA, September 2009Condensed Matter Group, University of Minnesota, Minneapolis, USA, October 2009.

M. Kafesaki

Sandia National Labs, Albuquerque, New Mexico, USA, February 2010US Air Force, Wright Patterson AFB, Dayton, Ohio, USA, May 2010

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3. Deliverables and milestones tables

Deliverables (excluding the periodic and final reports)

TABLE 1. DELIVERABLES5

Del. no.

Deliverable name WP no.

Lead beneficiay Nature Dissemination

levelDelivery date from Annex I (proj month)

DeliveredYes/No

Actual / Forecast delivery date

Comments

D7 2nd annual progress report

WP1-WP5

FORTH R CO, PU 24 Yes July 20, 2010

D8 Assessment of luminescent/gain materials incorporated into PMMs.

WP2-WP3

KIT-U R CO, PU 24 Yes July 20, 2010

D9 Blueprints of ICT relevant demonstrators

WP1- WP3

BILKENT R CO, PU 24 Yes July 20, 2010

D10 Fabrication and optical chracterization of bulk chiral PMMs

WP2- WP3

KIT-U R CO, PU 24 Yes July 20, 2010

Accomplishment of the deliverables D8: Assessment of luminescent/gain materials incorporated into PMMs See the separate report on D8 D9: Blueprints of ICT relevant demonstrators See the separate report on D9 D10: Fabrication and optical characterization of bulk chiral PMMs See the separate report on D10

5 For Security Projects the template for the deliverables list in Annex A1 has to be used.

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4. Project management

Dissemination

Below we mention some steps, planned or done, towards dissemination and use of the PHOME results. There is also a publication list and a list of conference presentations.

We have created a web page where we plan to put our articles on PMMs and our main results. This page is linked to the CORDIS sites, it gives links to the main groups working on the area of metamaterials and it will be connected also to the main metamaterial related web pages in the near future.

We present and we will continue to present the PHOME results through publications, colloquia, and participations to conferences and workshops.

We have organized sessions devoted to PMMs at international conferences (ETOPIM 8, Rethymnon, Crete, Greece, June 2009; SPIE 2009, San Diego, USA, August 2009; Metamaterials Congress Conference, London, UK September 2009; Medi-Nano 2, Athens, Greece, October 2009; TaCoNa-Photonics, Bad-Honnef, Germany, October 2009, MRS Fall Meeting, Boston, USA December 2009; 40th Winter Colloquium of Quantum Electronics, Snowbird, USA, January 2010; META’10, Egypt, Cairo, February 2010), where PHOME results have been advertised.

The experimental group of Karlsruhe is in discussion with industries about potential applications of PMMs as optical isolators.

We plan to send any information (high level publication, appearances of FET projects etc.) to the DG Information Society.

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5. Explanation of the use of the resources

This session will be added at a later stage, after all financial items will be compiled

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR COORDINATOR (FORTH) FOR THE PERIOD

Work Package

Item description Amount Explanations

1, 2, 3, 4 Personnel costs 84651,38 € Salaries for PhD students (9124 € - equivalent to one full time PhD student for 9 months), post docs (16059 € - full coverage of one post-doc for 12 months and a second post-doc for 7 months) and senior scientists (59468 € - partial support, equivalent to 11 full person months)

4 Travel expenses 14124,11 € Participation of two people in the Metamaterials conference and the PHOME 1st review meeting in London (4703 €), and in the 2nd PHOME meeting in Ankara (2572 €). Visit of C. Soukoulis to Karlsruhe and Amsterdam for collaboration (2505 €).Participation of C. Soukoulis in a Conference in Delpphi, Greece (~1000 €)Travelling and accommodation of C. Soukoulis, Th. Koschny and T. Gundogdu within Greece, for participation discussions and collaborations (~3000 €); host of visitors for discussion and collaborations (~1000 €)

2, 3 Consumables 4586,81 € Photolithography masks, wafers and chemicals for lithography processes, computer accessories.

4 Other 4220,16 € Costs for the organization of the ETOPIM8 conference, where most of the sessions were devoted to metamaterials

Remaining direct costsTOTAL DIRECT COSTS6 107582,46 €

* The entries in italics are examples and purely for illustration

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR IMPERIAL FOR THE PERIOD

Work Package

Item description Amount Explanations

1 Personnel costs €41,070.98 RA for 12 months4 Conference fees, Travel €4,776.63 SPIE photonics conference (Brussels,

Belgium)Plasmonics UK meeting (London)Gordon Conference in Plasmonics (ME, USA)Phome meeting (Karlsruhe, Germany)

6 Total direct costs have to be coherent with the directs costs claimed in Form C

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1,4 Consumables €1,563.34 Publication charges, Posters printing

TOTAL DIRECT COSTS7 €47,410.95

Deviations from the initial plan for Imperial: There is under-spending in the Imperial budget. We would like to proceed to discussions for transfer of part of Imperial budget to other partners.

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR BILKENT FOR THE PERIOD

Work Package

Item description Amount Explanations

1, 2, 3 Personnel costs 55.524,63 € Salaries of 2 postdoctoral researchers (for total 8 months) and one research associate (for 7 months)

1, 2 Travel expenses 13.790,37 € 1 researcher to 3rd Int Congress on Advanced Materials in Microwave and Optics, September 2009, London England (1.840 €)

E.Ozbay September 2009 Project Review Meeting, London-England and October 2009 Project Meeting Athens-Greece (2.800 €)

PHOME project meeting expenses, May 2009, Ankara Turkey (5.960 €)

2 researchers to Summer School on Plasmonics, September 2009, France (2.580 €)

1 researcher to research visit to FORTH, October 2009, Crete, Greece (600 €)

1, 2, 3 Consumables 25.306,16 € Simulation program annual fee and key fee (~1.400 €)

Consumables for the production of various metamaterial structures which are made of multiple layers of dielectric-metal composite structures. These consumables include FR4, Teflon and Rogers substrates, electromagnetic absorbers and the micromachining costs for these printed circuit board based structures. (~15.500 €)

Consumables for micro-nanofabrication of various photonic metamaterial structures. These include photomasks, e-beam lithography consumables, micro-nanofabrication chemicals and substrates. (~8.400 €)

1, 2, 3 Remaining direct costs

TOTAL DIRECT COSTS8 94.621,15 €

Deviations from the initial plan for Bilkent: The personnel budget was underspent in our first year. In the second year of the PHOME project, Bilkent’s research efforts were accomplished by our personnel that were being paid from the project. The personnel budget is now along our earlier predictions. The travel budget for

7 Total direct costs have to be coherent with the directs costs claimed in Form C8 Total direct costs have to be coherent with the directs costs claimed in Form C

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the first year was also below the projections and in the second year we have attended several meetings and we also had training related visits. The total travel budget is now along our earlier predicitions. As our e-beam lithography system is newly purchased, our consumable expenses for the first year was alot less than projections. As can be seen from our report, the nanolithography efforts were quite intense in our 2 nd year and the total consumable budget is near our projections.

TABLE: 3.1Personnel, subcontracting and other major direct cost items for UniKarl for this periodWork package Item description Amount ExplanationWP2 & WP3 Personnel costs 63.084,26 € Salary of 2 researchers for 7 months

(from 01/06/2009 to 31/12/2009)WP2 & WP3 Personnel costs 33.083,46 € Salary of 2 researchers for 5 months

(from 01/01/2010 to 31/05/2010)WP3 Equipment 2.619,54 € Optical componentsWP4 Travelling costs 4.161,30 € Travelling costs (conferences)WP5 Travelling costs 889,13 € Travelling costs (PHOME project

meeting)

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6. Appendices

Appendix A: Report of the Partner Imperial, on WP1.(This report is placed as appendix, due to the fact that most of the related work is still unpublished)

Summary of the work performed

Over the last year, we have shown how transformation optics can be used to design and study analytically novel plasmonic structures showing spectacular nanofocusing abilities. The proposed plasmonic nanostructures may find great potential applications in solar cells, surface enhanced Raman scattering (SERS), single molecular detection and non-linear optics. Ideally a plasmonic device should have a large cross-section and operate efficiently over a broad continuous spectrum. The latter is a severe challenge for small devices which tend to be efficient collectors at just a few resonant frequencies. To circumvent that issue, we propose to start from an infinite plasmonic system that naturally shows a broadband spectrum. Then, a singular conformal transformation is applied and converts the infinite structure into a finite one whilst preserving the broad band properties. Following this strategy, two devices are studied analytically: a cylinder with a crescent shaped cross-section and a device made of two kissing cylinders (see Fig.1).

FIG.1: Top: a thin layer of metal (a) and two semi-infinite metallic slabs separated by a thin dielectric film (b) support surface plasmons that couple to a dipole source, transporting its energy to infinity. The spectrum is continuous and broadband therefore the process is effective over a wide range of frequencies. Bottom: the transformed materials of (a) and (b) are now a cylinder with cross section in the form of a crescent and two kissing cylinders, respectively. The dipole source is transformed into a uniform electric field

Both plasmonic devices are shown to exhibit a large and continuous absorption cross-section relative to their physical size over the whole visible spectrum. They are also strong far-field to near-field converters of energy: considerable field enhancement (superior to 104) and confinement at the nano-scale are expected in the vicinity of the structure singularity (see Figs.2 and 3). This theoretical work is only valid upon the near-field approximation, hence radiation losses have also been investigated both analytically and numerically in those structures. Both devices are shown to keep a significant superfocusing behavior up to a dimension of 400 nm.

FIG.2: Amplitude of the x'-component of the electric field normalized by the incoming field. The left and right panels display the field in the crescent and in the kissing cylinders, considering silver at ω=0.9ωsp. As surface

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plasmons approach the structure singularity. their wavelength shortens and velocity decreases in proportion, leading to an energy accumulation.

FIG.3: Amplitude of the x'-component (blue) and the y'-component (red) of the electric field at the surface of the cylinder, plotted as a function of the angle, θ, defined in the figure, for ω=0.7ωsp. and ε = −8.3+0.29i taken from Johnson and Christy. Both curves are normalized to the incoming field amplitude E0. The field enhancement is the result of a balance between energy accumulation and dissipation losses. Note that the field enhancement is here considerable, exceeding a value of 104.

Transformation optics has also been applied to study well-known plasmonic structures for which no analytical model had been proposed until now. For instance, the physics of the interaction between two nanoparticles has been revisited with conformal transformation. Novel physical insights have been provided as regards the resonant behavior and the nanofocusing properties that may exhibit nanoparticle dimers (see Fig.4).

FIG. 4: Absorption cross-section as a fraction of the physical cross-section as a function of ρ=δ/2D and frequency for a cylinders pair with Do=20 nm. δ is the gap between the two nanoparticles, D the cylinder diameter and Do the overall physical cross-section. The color bar is in log-scale. The metal is assumed to be silver with permittivity taken from Johnson and Christy. The absorption cross-section shows several resonance denoted by index n that shift towards red when the gap between the two nanoparticles decreases.

Finally, 2D wedge-like structures, tapered wave guides, open nanocrescents or overlapping cylinders have been also investigated. Interestingly, these structures exhibit singularities where a divergence of the electric field may arise even in presence of dissipation losses. This divergent behavior had not been pointed out in the past and shows why our analytical approach is of significant interest compared to numerical studies.

Significant results obtained

Using transformation optics, various plasmonic structures have been designed and studied analytically, whereas, until now, only the numerical tool was available for the study of such plasmonic devices.

Nanostructures like a cylinder with a crescent-shaped cross-section or kissing cylinders are powerful light harvesting devices over a broadband spectrum, both in the visible and near infrared spectra.

These nanostructures exhibit considerable nanofocusing capabilities: our theory predicts a field enhancement that can go beyond a factor of 104 over a broadband spectrum.

10-1

10-0.5

100

10-1.5

10-2

10-2.5

=0.01

=0.1

=0.001

100.5

n=1n=2

n=3

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Radiation losses have been investigated both numerically and analytically in these devices. A good robustness relative to radiation losses has been predicted for structure dimension up to 400 nm.

The physics of the interaction between plasmonic nanoparticles has been revisited with transformation optics. Novel physical insights have been provided regards the resonant behavior of these nanostructures and the nanofocusing properties that can be expected with nanoparticle dimers.

2D wedge-like structures, tapered wave guides, open nanocrescents or overlapping cylinders are shown to exhibit a singularity, which may give rise to a divergence of the electric field, even in presence of dissipation losses. This singular behavior had not been pointed out in the past and can be of great interest for single molecule detection.

Description of the work performed

This reporting period we focused on the following issues1. Plasmonic light harvesting devices over a broadband spectrum2. A broadband plasmonic device concentrating the energy at the nanoscale: The crescent-

shaped cylinder3. Broadband nanofocusing of light using kissing nano-wires4. Interaction between plasmonic nanoparticles revisited with transformation optics5. Surface Plasmons and Singularities

1. Plasmonic light harvesting devices over a broadband spectrum

Abstract: Based on conformal transformation, a general strategy is proposed to design plasmonic nanostructures capable of an efficient harvesting of light over a broadband spectrum. The surface plasmon modes propagate towards the singularity of these structures where the group velocity vanishes and energy accumulates. A considerable field enhancement and confinement is thus expected. Radiation losses are also investigated when the structure dimension becomes comparable to the wavelength.

Reference: A. Aubry, D.Y. Lei, A. I. Fernandez-Dominguez, Y. Sonnefraud, S. A. Maier and J. B. Pendry, Nano Letters, in press, 2010

2. A broadband plasmonic device concentrating the energy at the nano-scale: The crescent-shaped cylinder

Abstract:A new strategy has been proposed recently to design plasmonic nanostructures capable of an efficient harvesting of light over a broadband spectrum. Applying a singular conformal transformation to a thin metal film, a cylinder with a crescent shaped cross-section is obtained. The behaviour of surface plasmons in this complex geometry is investigated

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analytically by solving the tractable slab problem. This nanostructure is shown to exhibit a large and continuous absorption cross-section relative to its physical size over both the visible and near-infrared spectra. This is also a strong far-field to near-field converter of energy: considerable field enhancement and confinement at the nano-scale is expected. Actually, instead of transporting the energy out to infinity, like in a metal slab geometry, the surface plasmon modes here propagate towards the crescent tips where the group velocity vanishes and energy accumulates. The nanofocusing performance of the crescent results from a balance between this energy accumulation and the dissipation losses. Numerical simulations have also been performed to investigate the effect of radiative losses when the structure dimension becomes comparable to the wavelength.

Reference: A. Aubry, D.Y. Lei, S. A. Maier and J. B. Pendry, submitted to Phys. Rev. B, 2010

3. Broadband nano-focusing of light using kissing nano-wires

Abstract:A strategy is proposed to design a plasmonic nanostructure capable of an efficient harvesting of light over a broadband spectrum. Applying a singular conformal transformation to a metal-insulator-metal infinite structure, two kissing cylinders are obtained. This nanostructure is shown to exhibit a large and continuous absorption cross-section relative to its physical size over the whole visible spectrum. This is also a strong far-field to near-field converter of energy: considerable field enhancement and confinement at the nano-scale is expected. Actually, instead of transporting the energy out to infinity, like in a metal slab geometry, the surface plasmon modes here propagate towards the touching point where their velocity vanishes and energy accumulates. The field enhancement is then a balance between this energy accumulation and dissipation losses. The asymptotic case of a nanowire placed on top of a metal plate is shown to be of special interest for nanofocusing. Numerical simulations have also been performed to investigate the effect of radiative losses when the structure dimension becomes comparable to the wavelength.

Reference: D.Y. Lei, A. Aubry, S. A. Maier and J. B. Pendry, to be submitted to Small, 2010

4. Interaction between plasmonic nanoparticles revisited with transformation optics

Abstract:Our canonical system is an array of dipoles placed between two semi-infinite metallic slabs . Applying a conformal transformation the semi-infinite slabs of metal are transformed into a pair of metallic cylinders. One the one hand, transformation optics provides a qualitative description of the surface plasmon modes propagating in such a dimer. On the other hand, by solving the problem in the original frame, one can deduce the analytical solution in the transformed geometry under the electrostatic approximation. Thus, we first study the coupling of an array of dipoles with the surface plasmons supported by two semi-infinite slabs of metal. Then, by applying a conformal transformation to this system, we deduce the behavior of surface plasmons in a pair of cylinders and their coupling with the external field The

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absorption spectrum is shown to exhibit several resonances which shift towards red when the gap between the two nanowires decreases. Conformal transformation provides an elegant tool to describe the physical mechanism responsible for the surface plasmon resonances engendered in the nanoparticle pair. The surface plasmons are shown to propagate along the surface of the cylinders. In the gap separating the two nanoparticle, the surface plasmons supported by each nanopatricle couple to each other: their wavelength as well as their group velocity decrease and an important field enhancement is then expected in the narrow gap separating the nanowires. At last, the question of radiative losses is raised when the structure size becomes comparable to the wave length. A theoretical correction is made on the electrostatic result to take into account radiation damping. Our analytical predictions are compared to numerical simulations.

Reference: A. Aubry, D.Y. Lei, S. A. Maier and J. B. Pendry, to be submitted to Phys. Rev. B, 2010

5. Surface plasmons and singularities

Abstract:We use transformation optics to design singular plasmonic structures for the broadband harvesting of light. Starting from a simple canonical structure for which analytic solutions are available we transform to a variety of 2-dimensional structures, including sharp edges, touching surfaces, and crescents, which concentrate the captured light at a singular point. Our analysis gives a unique insight into the capture process and holds the promise of detection of single molecules and greatly enhanced non linear effects.

Reference: Yu Luo, J.B. Pendry, and A. Aubry, submitted to Phys. Rev. Lett, 2010

Future plans

Until now, our strategy has only concerned 2D nanostructures. A future plan is to extend our theory to 3D. Albeit more complex, the 3D problem can still be solved by means of a conformal transformation which can relate, for example, kissing spheres to a slab problem.

The nanostructures we have studied derive from infinite metal slab structures through conformal transfomation. As a metal slab is a perfect lens under the near-field approximation, the transformed nanostructures may also act as curved perfect lenses. Hence a second plan will consist in studying the imaging properties of such devices.

A third plan is to study the combination of our nanostructures with gain material. As a drastic nanofocusing is observed with our nanostructures, one can expect strong non linear feature if a gain material is placed at the vicinity of the structure singularity. A theoretical study would allow to estimate if this combination could be of significant interest to circumvent the issue of losses in metamaterials.

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Appendix B: Deliverables

In the next pages the following deliverables have been appended:

Deliverable 8: Assessment of luminescent/gain materials incorporated in to photonic metamaterials

Deliverable 9: Blueprints of ICT relevant demonstrators

Deliverable 10: Fabrication and optical characterization of bulk chiral photonic metamaterials

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Deliverable 8: Assessment of luminescent/gain materials incorporated into photonic metamaterials

As pointed out in the original PHOME proposal, reducing or eliminating the losses of metamaterials operating at optical or even at visible frequencies is possibly the main challenge of the entire field of electromagnetic metamaterials.

At first sight, compensating the known levels of losses in photonic metamaterials by incorporating gain materials seems simply hopeless. However, as we have pointed out by collaborative theoretical publications [D8:1,D8:2] of the KIT and the FORTH partner in PHOME, plasmonic local-field effects can drastically enhance the effective gain as compared to the plain bulk material gain. Enhancement factors on the order of 10 appear to be within reach for realistic parameters. In contrast to all previous publications, KIT and FORTH have treated the problem of the metamaterial coupled to a gain material self-consistently – first on an approximate analytical level [D8:1] and later on a numerically exact level using a four-level system as a representative model for the gain [D8:2]. Reference [D8:1] has treated a 3D situation, [D8:2] a 2D model. Full 3D calculations have not been published by anybody so far. Such demanding numerical calculations are in progress at the FORTH partner.

With regard to experiments, KIT jointly with FORTH has followed an approach based on semiconductor gain as theoretically investigated in Ref.[D8:1]. Semiconductors rather than, e.g., dye molecules investigated by others (V.M. Shalaev’s group at Purdue university), are chosen in PHOME because semiconductors enable long-term use (dye molecules photo-bleach rapidly) and because semiconductors can conceptually be pumped by electrical injection. This is crucial as applications based on optically pumped structures do not appear to be realistic in the long run. Nevertheless, as outlined in the original PHOME proposal, early exploratory experiments have been performed under conditions of optical pumping.

In preparation of the work regarding gain, the KIT partner has fabricated many split-ring resonator (SRR) array structures on crystalline GaAs semiconductor substrates [D8:3] using electron-beam lithography. Clearly, due to the higher average refractive index of the SRR environment, the SRR lateral size has to be further reduced compared to our previous structures on glass substrates to reach the same operation frequency – posing a certain challenge for nanofabrication that we have solved. We indeed find strong coupling between the electromagnetic near-fields of the split rings and the underlying GaAs substrate, resulting in measured second-harmonic generation (SHG) that is about 25 times stronger than that we have previously found for split-ring-resonator arrays on glass substrate [D8:4]. Specifically, accounting for a necessary MgF2 spacer layer (to avoid quenching and gold diffusion), the intensity enhancement can be 25-fold [D8:3], resulting in a substantial local increase of the SHG source term – a highly encouraging experimental result.

On a large variety of wafers that were provided by collaborators G. Khitrova and H. Gibbs at the Optical Sciences Center in Tucson (U.S.A.), the KIT partner has fabricated gold SRR arrays (again by using electron-beam lithography, high-vacuum gold evaporation, and a lift-off procedure). On each wafer, a systematic series of arrays with different SRR resonance wavelengths has been fabricated, allowing for tuning SRR and gain resonances with respect to each other. Furthermore, a dedicated low-temperature femtosecond pump/probe experiment has been assembled. In this setup, pulses centered around 800-nm wavelength derived from a Ti:sapphire laser are used as the optical pump. Average powers around 100 mW focused to spots on the sample with diameters around 20-30 µm enable extremely strong pumping

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conditions, for which quantum well (QW) gain is expected. Fortunately, under these intense, essentially continuous-wave, pumping conditions, no sample deterioration has been observed. The probe pulses are derived from an optical parametric oscillator (OPO) that is tunable at around 1500-nm wavelength. The setup allows for detecting pump-induced changes in transmittance. The samples are cooled in a He-flow cryostat to increase the anticipated material gain.

The KIT partner has systematically measured a vast variety of samples and configurations [D8:5]. So far, the most consistent results have been obtained on a single-QW sample, the low-temperature photoluminescence of which is centered at around 1450-nm wavelength (which also matches best the tuning range of the OPO). At present, we do not have a complete understanding of the highly complex behavior. However, the following aspects can be regarded as preliminary experimental evidence.

Figure D8.1: Electron micrograph of an array of magnetic gold split-ring resonators with resonance frequencies at around 1.5 µm wavelength fabricated on top of a single QW semiconductor wafer by using electron-beam lithography.

First, we find differential transmittance signals on the SRR arrays that are up to an order of magnitude larger (T/T=5 %) than for the bare QW (T/T=0.5 %). This finding is consistent with the expectation of an effective gain that is larger than the bare QW gain being brought about by the local-field enhancement of the SRR (as expected from Refs.[D8:1,D8:2]). Indeed, as a control, this enhancement disappears for off-resonant SRR arrays. Forming another control, it also disappears for the orthogonal linear probe polarization, for which the light does not efficiently couple to the SRR.

Second, we find a much more rapid dynamics on the SRR arrays compared to on the bare QW. Again, this finding is consistent with a substantial coupling of gain and SRR. Depending on the probe wavelength, the decay times can become as short as just a few picoseconds, which has to be compared to the decay for the bare QW of some hundreds of picoseconds. Quenching due to the close proximity of the gold can be ruled out as the origin of this rapid decay because the decays on the same SRR arrays but for the orthogonal linear probe polarization show pretty much the same behavior as for the bare QW sample.

Third, the observed temporal decays depend very sensitively on probe wavelength, indicating some sort of a resonance (as anticipated in Ref.[D8:1]). It is presently not clear, however, whether we observe indications of the desired strong coupling between SRR and QW gain.

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Possibly, the 20-nm broad OPO spectrum (corresponding to about 150-fs pulses) also averages over yet finer details. This aspect needs to be further investigated.

In summary, we consider these experimental results as highly encouraging as they have already indicated the anticipated (and needed) enhancement of the QW gain by local-field effects. With an improved understanding, on the basis of which new wafers can be designed and fabricated, metamaterial loss compensation might actually come into reach.

It has been clear from the start that this aspect of PHOME is extremely risky. However, solving the main challenge of the field of metamaterials in the future could also be very highly rewarding.

References D8[D8:1] M. Wegener, J.L. Garcia Pomar, C.M. Soukoulis, N. Meinzer, M. Ruther, and S. Linden, Toy model for plasmonic metamaterial resonances coupled to two-level system gain, Opt. Express 16, 19785 (2008)

[D8:2] A. Fang, Th. Koschny, M. Wegener, and C.M. Soukoulis, Self-consistent calculation of metamaterials with gain, Phys. Rev. B 79, 241104(R) (2009)

[D8:3] F.B.P. Niesler, N. Feth, S. Linden, J. Niegemann, J. Gieseler, K. Busch, and M. Wegener, Second-harmonic generation from split-ring resonators on a GaAs substrate, Opt. Lett. 34, 1997 (2009)

[D8:4] N. Feth, S. Linden, M.W. Klein, M. Decker, F.B.P. Niesler, Y. Zeng, W. Hoyer, J. Liu, S.W. Koch, J.V. Moloney, and M. Wegener, Second-harmonic generation from complementary split-ring resonators¸ Opt. Lett. 33, 1975 (2008)

[D8:5] N. Meinzer, M. Ruther, S. Linden, M. Wegener, and C.M. Soukoulis, unpublished (2010)

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Deliverable 9: Blueprints of ICT relevant demonstrators

As pointed out in the original PHOME proposal, using chiral metamaterials can be used as thin-film optical isolators. In addition, we have proposed to use photonic metamaterials that can be used as tunable switches at THz frequencies, and finally we have proposed to use photonic metamaterials for electro-optic modulation.

Chirality only exists in truly three-dimensional structures, i.e., it does not occur in planar metamaterials. Furthermore, chirality enables devices that are immediately relevant for ICT-related applications such as, e.g., “poor man’s optical isolators” or circular polarization filters. Combined with non-reciprocal constituent materials, chirality would also enable true optical isolators based on the Faraday effect in the future. In Fig. 9 we present the designs and the fabricated samples for GHz and THz frequencies [D9:1, D9:2, D9:3, D9:4, D9:5, D9:6]. Notice that

Figure 9.1: Comparison of different chiral metamaterials, which were fabricated and experimentally characterized at GHz and THz frequencies.

the rotation angle per wavelength is around 800o for GHz frequencies, around 400o for 3 microns and around 60o for 1.5 microns. The rotation angle is given with zero ellipticity, i.e. it means that the linear polarized wave rotates and remains linear polarized. These new designs, which have been fabricated and measured experimentally, can be used as thin-film optical isolators.

The second ICT demonstrator is the gold-helix metamaterial that was fabricated [D9:7] with direct laser writing (DLW) and it was filled with gold using an electroplating approach. This

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work can be viewed as a possible first “real-world” application of the far-reaching concepts of electromagnetic metamaterials.

The realized gold-helix metamaterial can serve as a compact broadband (more than one octave bandwidth) circular polarizer that might find applications in infrared spectroscopy of fingerprints of chiral molecules. Importantly, a linear polarizer and a subsequent quarter-wave plate cannot simply obtain broadband circular polarization of light. The realized structures [D9: 7] can be viewed as the circular analogue of the good old wire-grid polarizer that is widely applied for obtaining linear polarization of light.

The third ICT demonstrator is the dynamic response of metamaterials at

the THz regime. In particular we have made designs, fabricated the samples and characterize them by THz time-domain spectroscopy. We demonstrate experimentally [D9:8] blueshift tunability and a broadband phase modulation. This happens when the metamaterial is dynamically photoexcited, using synchronized femtosecond near-infrared laser pulses. The possibility of phase modulation under photoexcitation, opens the way of realization of broadband (250 GHz) phase plate devices in the THz range. In addition, we have designed and fabricated [D9:9] a new metamaterial device that gives a dual-band switch, which has a lot of potential applications in switchable devices.

Fig. D9.3: Schematic view of our design for broadband blue-shift tunable metamaterial.

Fig. D9.4: Optical microscopy image of the fabricated metamaterial device.

Figure D9.2: 3D gold-helix metamaterial serving as compact, broadband circular polarizer [D9:7].

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Fig. D9.5: Simulation results of transmission with different conductivity levels of photoactive silicon.

Fig. D9.6: Experimentally measured transmission for different levels of energy flux of pump beam.

References D9[D9: 1] E. Plum, J. Dong, J. Zhou, V. A. Fedotov, Th. Koschny, C. M. Soukoulis, and N. I. Zheludev, “Metamaterial with Negative Index due to Chirality,” Phys. Rev. B. 79, 035407 (2009); (Selected for a Viewpoint in Physics 2, 3 (2009)).

[D9:2] J. Zhou, J. Dong, B. Wang, Th. Koschny, M. Kafesaki and C. M. Soukoulis, “Negative refractive index due to chirality,” Phys. Rev. B. 79, 121104(R) (2009).

[D9:3] M. Decker, M. Ruther, C.E. Kriegler, J. Zhou, C.M. Soukoulis, S. Linden, and M. Wegener, “Strong optical activity from twisted-cross photonic metamaterials,” Optics. Letters 34, 2501(2009).

[D9:4] Z. Li, R. Zhao, Th. Koschny, M. Kafesaki, E. Colak, H. Caglayan, E. Ozbay and C. M. Soukoulis, “Chiral metamaterials with negative refractive index based on Four-U-SRRs resonators,” Appl. Phys. Lett. (submitted).

[D9:5] M. Decker R. Zhao, C.M. Soukoulis, S. Linden, and M. Wegener, “Twisted split-ring-resonator photonic metamaterial with huge optical activity,” Opt. Lett. 35, 1593 (2010).

[D9:6] R. Zhao, Th. Koschny and C. M. Soukoulis, “Conjugated-bi-layer swastika-shaped chiral metamaterial with huge optical activity and negative refractive index,” unpublished.

[D9:7] J.K. Gansel, M. Thiel, M.S. Rill, M. Decker, K. Bade, V. Saile, G. von Freymann, S. Linden, and M. Wegener, Gold helix photonic metamaterial as broadband circular polarizer, Science 325, 1513 (2009).

[D9:8] J. M. Manceau, N.-H. Shen, M. Kafesaki, C. M. Soukoulis, and S. Tzortzakis, “Dynamic response of metamaterials in the terahertz regime: Blue shift tunability and broadband phase modulation,” Appl. Phys. Lett. 96, 021111 (2010).

[D9:9] N.-H. Shen, M. Massaouti, M. Gokkavas, E. Ozbay, J. M. Manceau, S. Tzortzakis, and C. M. Soukoulis, “Experimental realization of broadband blue-shift swith in THz regime with all optical implementation,” unpublished

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Deliverable 10: Fabrication and optical characterization of bulk chiral photonic metamaterials

Chirality only exists in truly three-dimensional structures, i.e., it does not occur in planar metamaterials. This makes chirality an ideal test ground for three-dimensional metamaterials from a scientific viewpoint. Furthermore, chirality enables devices that are immediately relevant for ICT-related applications such as, e.g., “poor man’s optical isolators” or circular polarization filters. Combined with non-reciprocal constituent materials, chirality would also enable true optical isolators based on the Faraday effect in the future.

Chirality requires magnetic dipoles excited by the electric component of the light field [D10:1] and vice versa and is thus intimately related to the magnetic metamaterials reported in deliverable D4. Chiral metamaterials are a subclass of bianisotropic metamaterials [D10:2,D10:3,D10:4,D10:5] that we have also successfully investigated in PHOME.

Figure D10.1: 3D chiral photonic metamaterial composed of twisted crosses [D10:6].

The fabrication of three-dimensional metamaterial structures with optical operation frequencies poses a significant challenge to nanofabrication. In collaboration of the PHOME partners, we have successfully followed two different complementary routes, namely (i) stacking of different layers made via electron-beam lithography and intermediate planarization and (ii) direct laser writing of three-dimensional structures.

(i) Based on this more conservative approach, we have designed (FORTH and KIT), fabricated (BILKENT and KIT), and characterized (KIT) chiral metamaterials.

The first example [D10:6] is a design developed by FORTH that is based on twisted crosses as the meta-atoms. These structures exhibit strong and pure optical activity in a fairly large spectral range at around 1.3 µm wavelength. Specifically, the differences of the refractive indices for the two circular polarizations are as large as |n|=0.35 and intensity conversion of circular polarization is smaller than 10-3. Importantly, negligible conversion implies that the circular polarizations are actually the good eigenpolarizations.

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The second design [D10:7] based on dimers of twisted split-ring resonators (SRR) was also stimulated by a theoretical suggestion from the FORTH partner. Experiments were performed at both KIT and BILKENT. Here, yet stronger optical activity has been found at wavelengths around 3 µm. The differences between the two circular refractive indices have reached values as large as large as |n|=2. Linear birefringence is intentionally suppressed by a suitable laterally extended unit cell of the SRR dimers, recovering four-fold rotational symmetry.

Figure D10.2: 3D chiral photonic metamaterial composed of twisted split-ring resonators [D10:7].

For both of these examples, lithographic alignment accuracies between the two layers of just a few nanometers were required and achieved. Furthermore, both experiments required appropriate optical characterization with incident circular polarization of light that was developed by the KIT partner in workpackage WP3.

(ii) The fabrication of three-dimensional (3D) photonic metamaterials on the basis of direct laser writing by the KIT partner had to be considered as highly risky at the start of the PHOME project. Direct laser writing (DLW) can be viewed as the three-dimensional analogue of electron-beam lithography. Fabrication of polymer structures by this approach has become standard. In fact, the KIT partner has been using a commercial instrument from Nanoscribe GmbH (a collaboration with Carl Zeiss) that has emerged out of previous Karlsruhe work. In contrast, infilling or coating of such 3D polymer structures with metals has not been standard at all at the beginning of PHOME. Coating approaches using chemical vapor deposition have successfully been developed [D10:2,D10:3, D10:4,D10:5]. More recently, infilling with gold using an electroplating approach has turned out to be highly attractive [D10:8]. This work can be viewed as a possible first “real-world” application of the far-reaching concepts of electromagnetic metamaterials. The realized gold-helix metamaterial can serve as a compact broadband (more than one octave bandwidth) circular polarizer that might find applications in infrared spectroscopy of fingerprints of chiral molecules. Importantly, broadband circular polarization of light cannot simply be obtained by a linear polarizer and a subsequent quarter-wave plate. The realized structures [D10:8] can be viewed as the circular analogue of the good old wire-grid polarizer that is widely applied for obtaining linear polarization of light.

The device performance can be improved systematically, e.g., by increasing the number of helix pitches – as outlined in a recent numerical design study [D10:9]. Interaction effects among the helices are important and can also be used as a design tool (also see [D10:11].

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The gold-helix metamaterials realized in Ref.[D10:8] are uniaxial. This is neither a problem for applications in terms of circular polarizers nor for “poor-man’s optical isolators”. However, for other applications, more isotropic chiral metamaterials may be desired. To this end, the KIT partner has suggested and realized by using DLW novel bi-chiral structures that are three-dimensionally isotropic in the long-wavelength limit [D10:10]. Yet larger operation bandwidth can be expected from chiral superlattices [D10:11] that have also been made by DLW. However, so far, these bi-chiral structures and chiral superlattices have only been realized in dielectric form (“photonic crystals”). Based on the approach of Ref.[D10:8], metallic versions can possibly be made within PHOME in the future.

Figure D10.3: 3D gold-helix metamaterial serving as compact, broadband circular polarizer [D10:8].

Finally, reaching beyond the original goals of PHOME and in collaboration between KIT and Imperial partners, first 3D invisibility cloaking structures have been realized [D10:12,D10:13] – another striking demonstration of the future possibilities of our direct laser writing approach (ii) for making 3D metamaterials at optical frequencies.

References D10

[D10:1] M. Wegener and S. Linden, Giving light yet another new twist, Physics 2, 3 (2009)

[D10:2] M.S. Rill, C. Plet, M. Thiel, I. Staude, G. von Freymann, S. Linden, and M. Wegener, Photonic Metamaterials by Direct Laser Writing and Silver Chemical Vapor Deposition, Nature Mater. 7, 543 (2008)

[D10:3] C.E. Kriegler, M.S. Rill, M. Thiel, E. Müller, S. Essig, A. Frölich, G. von Freymann, S. Linden, D. Gerthsen, H. Hahn, K. Busch, and M. Wegener, Transition between corrugated metal films and split-ring-resonator arrays, Appl. Phys. B 96, 749 (2009)

[D10:4] M.S. Rill, C.E. Kriegler, M. Thiel, G. von Freymann, S. Linden, and M. Wegener, Negative-index bianisotropic photonic metamaterial fabricated by direct laser writing and silver shadow evaporation, Opt. Lett. 34, 19 (2009)

[D10:5] C.E. Kriegler, M.S. Rill, S. Linden, and M. Wegener, Bianisotropic photonic metamaterials, IEEE J. Sel. Top. Quant. 16, 367 (2010)

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[D10:6] M. Decker, M. Ruther, C. Kriegler, J. Zhou, C.M. Soukoulis, S. Linden, and M. Wegener, Strong optical activity from twisted-cross photonic metamaterials, Opt. Lett. 34, 2501 (2009)

[D10:7] M. Decker, R. Zhao, C.M. Soukoulis, S. Linden, and M. Wegener, Twisted split-ring-resonator photonic metamaterial with huge optical activity, Opt. Lett., 35, 1593 (2010)

[D10:8] J.K. Gansel, M. Thiel, M.S. Rill, M. Decker, K. Bade, V. Saile, G. von Freymann, S. Linden, and M. Wegener, Gold helix photonic metamaterial as broadband circular polarizer, Science 325, 1513 (2009)

[D10:9] J.K. Gansel, M. Wegener, S. Burger, and S. Linden, Gold helix photonic metamaterials: A numerical parameter study, Opt. Express 18, 1059 (2010)

[D10:10] M. Thiel, M.S. Rill, G. von Freymann, and M. Wegener, Three-dimensional bi-chiral photonic crystals, Adv. Mater. 21, 4680 (2009)

[D10:11] M. Thiel, H. Fischer, G. von Freymann, and M. Wegener, Three-dimensional chiral photonic superlattices, Opt. Lett. 35, 166 (2010)

[D10:12] J.C. Halimeh, T. Ergin, J. Mueller, N. Stenger, and M. Wegener, Photorealistic images of carpet cloaks, Opt. Express 17, 19328 (2009)

[D10:13] T. Ergin, N. Stenger, P. Brenner, J.B. Pendry, and M. Wegener, Three-Dimensional Invisibility Cloak at Optical Wavelengths, Science 328, 337 (2010)

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Appendix C: Response to reviewers comments in the first year

Following the reviewers’ comments regarding the importance of “frequency-agile” optical metamaterials, the KIT partner in PHOME has started a corresponding effort that has been inspired by discussions with FORTH. Generally, there are two options: tuning/modulating the dielectric environment of the metal structure or tuning/modulating the metal properties themselves. In the PHOME work, inspired by previous work on “metallic muscles” (J. Weissmüller, et al. Charge-induced reversible strain in a metal, Science 300, 312-315 (2003)), we have followed the latter approach and have exposed extremely thin gold nanostructures to an aqueous NaF-based electrolyte. When varying the electrode potential by about 1 Volt, we observe that plasmonic resonances centered at around 300 THz shift by as much as 55 THz. The figure gives an impression of the magnitude of the effects observed on arrays of gold split-ring resonators. A corresponding manuscript will soon be submitted for publication as a Letter to Nature Materials.

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Following the reviewers’ comments regarding further enhancing the collaborations with the Imperial partner within PHOME, we have collaborated on 3D metamaterials for applications in first 3D invisibility cloaking structures based on transformations optics. This work has led to a collaborative publication between KIT and Imperial that recently appeared: T. Ergin, N. Stenger, P. Brenner, J.B. Pendry, and M. Wegener, Three-Dimensional Invisibility Cloak at Optical Wavelengths, Science 328, 337 (2010). This work has attracted tremendous (!) attention by the media all around the world. The underlying 3D direct laser writing technology is described in more detail in deliverable D10.

Last year the reviewers levelled the following criticisms as regards the Imperial College group:

“A better connection between the Imperial College group working on forward phase conjugation and the rest of the Consortium is desirable.”

“The novel approach involving forward phase-conjugation (that allows to harness gain) for realizing negative refraction should be more closely linked with other work elsewhere in the project.”

In reply to these criticisms, a collaboration started with Martin Wegener (Karlsruhe) on 3D metamaterials for applications in first 3D invisibility cloaking structures based on transformations optics. This work has led to a collaborative publication between KIT and Imperial that recently appeared: T. Ergin, N. Stenger, P. Brenner, J.B. Pendry, and M. Wegener, Three-Dimensional Invisibility Cloak at Optical Wavelengths, Science 328, 337 (2010). Further collaborations with the Wegener group will follow from their experimental work on chiral structures. Earlier theoretical work by ourselves (J.B. Pendry , A Chiral Route to Negative Refraction, Science 306 1353 (2004) ) indicated some exciting possibilities for such structures. FORTH, Bilkent and KIT-U are working to fabricate chiral structures that will give negative index of refraction, as was suggested by our partners at Imperial College.

As regards the phase conjugation work which was not enough collaborative, we decided to start a new project more related to the PHOME project dealing with transformation optics applied to plasmonics (see the progress report above). Novel plasmonic devices have been designed and studied analytically. They are efficient harvestors of light over a broadband spectrum capable of a considerable nanofocusing of light energy. Combing such nanostructures with gain materials may provide a solution to the issue of losses in metamaterials.