miniaturized multiphoton microscope with a 24hz frame-rate

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Miniaturized multiphoton microscope with a 24Hz frame-rate Tzu-Ming Liu 1 , Ming-Che Chan 1 , I-Hsiu Chen 1 , Shih-Hsuan Chia 1 , and Chi-Kuang Sun 1,2* 1 Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, TAIWAN. R.O.C. 2 Research Center for Applied Sciences, Academia Sinica, Taipei 11529, TAIWAN R.O.C. *corresponding author: [email protected] Abstract: With miniaturized tube lenses and a micro-electro-mechanical system (MEMS) mirror, we constructed a miniaturized multiphoton microscope system. Through a two-dimensional asynchronous scanning of the MEMS mirror, 24Hz frame rate can be realized. With a high numerical aperture objective, sub-micron resolution can also be achieved at the same time. ©2008 Optical Society of America OCIS codes: (180.4315) Nonlinear microscopy; (190.4710) Optical nonlinearities in organic materials; (190.3970) Microparticle nonlinear optics. References and links 1. L. Fu, A. Jain, H. Xie, C. Cranfield, and M.Gu, “Nonlinear optical endoscopy based on a double-clad photonic crystal fiber and a MEMS mirror,” Opt. Express 14, 1027-1032 (2006). 2. W. Piyawattanametha, R. P. J. Barretto, T. H. Ko, B. A. Flusberg, E. D. Cocker, H. Ra, D. Lee, O. Solgaard, and M. J. Schnitzer, “Fast-scanning two-photon fluorescence imaging based on a microelectromechanical systems two-dimensional scanning mirror,” Opt. Lett. 31, 2018-2020 (2006). 3. H. J. Shin, M. C. Pierce, D. Lee, H. Ra, O. Solgaard, and R. Richards-Kortum, “Fiber-optic confocal microscope using a MEMS scanner and miniature objectives lens,” Opt. Express 15, 9113-9122 (2007). 4. B. A. Flusberg, J. C. Jung, E. D. Cocker, E. P. Anderson, and M. J. Schnitzer, “In vivo brain imaging using a portable 3.9 gram two-photon fluorescence microscope ,” Opt. Lett. 30, 2272-2274 (2005). 5. W. Göbel, J. N. D. Kerr, A. Nimmerjahn, and F. Helmchen, “ Miniaturized two-photon microscope based on a flexible coherent fiber bundle and a gradient-index lens objective,” Opt. Lett. 29, 2521-2523 (2004). 6. J. C. Jung and M. J. Schnitzer,“Multiphoton endoscopy,” Opt. Lett. 28, 9902-904 (2003). 7. D. Bird and M. Gu, “Two-photon fluorescence endoscopy with a micro-optic scanning head,” Opt. Lett. 28, 1552-1554 (2003). 8. M. J. Levene, D. A. Dombeck, K. A. Kasischke, R. P. Molly, and W. W. Webb, “In vivo multiphoton microscopy of deep brain tissue,” J. Neurophysiol. 91, 1908-1912 (2003). 9. R. M. Williams, W. R. Ziptel, and W. W. Webb, “Interpretating second-harmonic generation images of collagen I fibrils,” Biophys. J. 88, 1377-1386 (2005). 10. T. A. Theodossiou, C. Thrasivoulou, C. Ekwobi, and D. L. Becker, “Second harmonic generation confocal microscopy of collagen type I from rat tendon cryosections,” Biophys. J. 91, 4665-4677 (2006). 11. L. Fu and M. Gu, “ Polarization anisotropy in fiber-optic second harmonic generation microscopy,” Opt. Express 16, 5000-5006 (2008). 1. Introduction Multi-photon nonlinear optical microscopy has emerged as one of the least-invasive tools to perform three dimensional imaging with a submicron resolution. Physiological and morphological changes of living cells can thus be visualized, providing disease diagnosis at an early stage. To further extend nonlinear optical imaging for hand-held or endoscopic applications, the bulky scanning system should be miniaturized to a compact one. In general, the development of the miniaturization includes two parts: one is the scanning unit and the other is the lens, including tube lenses and objectives. The miniaturization of scanning unit is usually based on the use of micro-electro-mechanical system (MEMS) mirrors [1-3], piezoelectric actuator driven fibers [4], or scanning on a fiber bundle [5]. The size reduction #91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008 (C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10501

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Miniaturized multiphoton microscope with a 24Hz frame-rate

Tzu-Ming Liu1, Ming-Che Chan1, I-Hsiu Chen1, Shih-Hsuan Chia1, and Chi-Kuang Sun1,2*

1 Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, TAIWAN. R.O.C.

2 Research Center for Applied Sciences, Academia Sinica, Taipei 11529, TAIWAN R.O.C. *corresponding author: [email protected]

Abstract: With miniaturized tube lenses and a micro-electro-mechanical system (MEMS) mirror, we constructed a miniaturized multiphoton microscope system. Through a two-dimensional asynchronous scanning of the MEMS mirror, 24Hz frame rate can be realized. With a high numerical aperture objective, sub-micron resolution can also be achieved at the same time.

©2008 Optical Society of America

OCIS codes: (180.4315) Nonlinear microscopy; (190.4710) Optical nonlinearities in organic materials; (190.3970) Microparticle nonlinear optics.

References and links

1. L. Fu, A. Jain, H. Xie, C. Cranfield, and M.Gu, “Nonlinear optical endoscopy based on a double-clad photonic crystal fiber and a MEMS mirror,” Opt. Express 14, 1027-1032 (2006).

2. W. Piyawattanametha, R. P. J. Barretto, T. H. Ko, B. A. Flusberg, E. D. Cocker, H. Ra, D. Lee, O. Solgaard, and M. J. Schnitzer, “Fast-scanning two-photon fluorescence imaging based on a microelectromechanical systems two-dimensional scanning mirror,” Opt. Lett. 31, 2018-2020 (2006).

3. H. J. Shin, M. C. Pierce, D. Lee, H. Ra, O. Solgaard, and R. Richards-Kortum, “Fiber-optic confocal microscope using a MEMS scanner and miniature objectives lens,” Opt. Express 15, 9113-9122 (2007).

4. B. A. Flusberg, J. C. Jung, E. D. Cocker, E. P. Anderson, and M. J. Schnitzer, “In vivo brain imaging using a portable 3.9 gram two-photon fluorescence microscope ,” Opt. Lett. 30, 2272-2274 (2005).

5. W. Göbel, J. N. D. Kerr, A. Nimmerjahn, and F. Helmchen, “ Miniaturized two-photon microscope based on a flexible coherent fiber bundle and a gradient-index lens objective,” Opt. Lett. 29, 2521-2523 (2004).

6. J. C. Jung and M. J. Schnitzer,“Multiphoton endoscopy,” Opt. Lett. 28, 9902-904 (2003). 7. D. Bird and M. Gu, “Two-photon fluorescence endoscopy with a micro-optic scanning head,” Opt. Lett.

28, 1552-1554 (2003). 8. M. J. Levene, D. A. Dombeck, K. A. Kasischke, R. P. Molly, and W. W. Webb, “In vivo multiphoton

microscopy of deep brain tissue,” J. Neurophysiol. 91, 1908-1912 (2003). 9. R. M. Williams, W. R. Ziptel, and W. W. Webb, “Interpretating second-harmonic generation images of

collagen I fibrils,” Biophys. J. 88, 1377-1386 (2005). 10. T. A. Theodossiou, C. Thrasivoulou, C. Ekwobi, and D. L. Becker, “Second harmonic generation confocal

microscopy of collagen type I from rat tendon cryosections,” Biophys. J. 91, 4665-4677 (2006). 11. L. Fu and M. Gu, “ Polarization anisotropy in fiber-optic second harmonic generation microscopy,” Opt.

Express 16, 5000-5006 (2008).

1. Introduction

Multi-photon nonlinear optical microscopy has emerged as one of the least-invasive tools to perform three dimensional imaging with a submicron resolution. Physiological and morphological changes of living cells can thus be visualized, providing disease diagnosis at an early stage. To further extend nonlinear optical imaging for hand-held or endoscopic applications, the bulky scanning system should be miniaturized to a compact one. In general, the development of the miniaturization includes two parts: one is the scanning unit and the other is the lens, including tube lenses and objectives. The miniaturization of scanning unit is usually based on the use of micro-electro-mechanical system (MEMS) mirrors [1-3], piezoelectric actuator driven fibers [4], or scanning on a fiber bundle [5]. The size reduction

#91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008

(C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10501

of the tube lens and the objective usually employ a gradient-index (GRIN) rod lens [1, 4-8]. These previous miniaturized demonstrations achieved three dimensional sectioning capabilities with a 1~2-micrometer transverse resolution. However most of the previous demonstrations employed a synchronous scanning scheme to acquire the data with a slow frame rate. For studying fast biological processes such as blood flow or neuronal activity, the frame rate should be enhanced. Recent advance in the technology of the MEMS mirror increase the resonant frequency of the mirror plate to several kHz on both axis. High frame-rate image acquisition can thus be achieved using high-resonant-frequency MEMS mirrors. By far, at best 8 frame/sec can be achieved in a MEMS-based fiber-optic confocal microscope system [3]. In this work, we employed a MEMS mirror with a high resonant frequency (9.8 KHz) to perform asynchronous scanning in a miniaturized nonlinear microscope system. Combined with a miniaturized tube lens and a focusing objective, the generated nonlinear signal are detected, sampled, and mapped to a 512×512-pixel reconstructed image. Without severe image distortion, record high 24 frame/sec frame-rate and submicron transverse resolution can be simultaneously achieved for the first time in a miniaturized nonlinear microscope.

2. Methods

The miniaturization of our nonlinear microscope system includes the use of a MEMS mirror and a size-reduced tube lens.

2.1 MEMS scanning scheme

The MEMS mirror is the key component that achieves imaging with a high frame rate (Fraunhofer Institut Photonische Mikrosysteme, 2D scanner). The mirror was resonantly and electrically driven by 2.475 kHz and 19.608 kHz square waves. The corresponding mechanical scanning frequency were fx=1.2375 kHz and fy=9.804 kHz, which has an even higher line scanning rate than a previous work [2]. This Lissajous-scanned frequency set were synchronously synthesized from the 50MHz-clock of a Field Programmable Gate Array (FPGA). Cascaded with electrical amplifiers, 0~50V driving voltages were applied to the MEMS mirror. When the MEMS mirror was driven at 50V, the incident laser beam can be sinusoidally deflected by 12 degrees for both axes. Imaged by a tube lens and an objective, the deflected laser beam will be focused on the focal plane of the objective lens and scanned

within a square area which is divided into 512×512 pixels. To scan through all the pixels, the highest possible frame rate is 24Hz. Different from the synchronous scanning scheme, the laser beam will not scan line-by-line on the focal plane of the objective lens. Before it scan

through a line, the trajectory of the laser beam will move to another line of the 512×512-pixel image. To reconstruct the detected data into an image, we simulate the trajectory of the laser beam and create a mapping table to transform the scanned vector data in a frame period into a

512× 512-pixel image. The mapping table is created by xn=256+256× sin(2πfxnΔt) and

yn=256+256×sin(2πfynΔt), where Δt is the sampling period and xn and yn are the pixel indices of the nth sampling, whose value will be round up or down into integer. However, the phase lag between the driving voltage and the mechanical response of the MEMS mirror will cause ghost images. This problem can be solved by cyclically rotating the vector xn and yn, by which the phase of the mapping function along x and y axes can by tuned. Ghost images can then be superimposed back to the correct ones.

2.2 Tube lens design

A tube lens was employed to image the laser beam spot on the MEMS mirror into the back aperture of the objectives. When the MEMS mirror scan, all of the deflected beams will be first collimated and then converged again onto the back aperture of the objective. Then these deflected beams were focused and scanned on the focal plane of the objective. To minimize

#91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008

(C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10502

the coma and the spherical aberration caused by the oblique incidence of the deflected laser beams, the radius of curvature (ROC) of both lenses were carefully designed and simulated by the ZEMAX software. In simulation and design, for different incident angles, the wavefront distortion resulted from aberration and coma was controlled within 4/λ. The focused spot size after objective lens was also controlled to be within 1μm. Under these design constraints, the image resolution and quality won’t be affected much by oblique incidence. The first lens is made of SF11 glass with 10.13mm ROC on the incident side and -8.813mm ROC on the other side. The effective focal length on the incident side of the first lens is 5mm. The second lens is made of BK7 with 38.24mm ROC on the incident side and -45.27mm ROC on the other side. Both lenses have 10mm diameter and 7mm thickness. The outer diameter of the whole tube lens module (including the mounting) is 3cm and the resulted magnification factor is 5.7. All the lenses are antireflection coated for the high transmission around 1250nm.

3. Experimental setup

Our high frame rate nonlinear optical imaging system is composed of a home build femtosecond Cr:forsterite laser source, the 2D MEMS scanning unit, the miniaturized tube lens pair, an objective, and a computer control system with a FPGA core (Fig. 1). The Cr:forsterite laser can typically deliver 500mW output power of 60fs pulses with 83MHz pulse repetition rate. Its 1250nm operating wavelength falls in the optical penetration window of most biological tissue. The mode locking of the laser system is kept stable with the help of a semiconductor saturable absorber mirror. Before delivering the laser beam to the MEMS mirror, we shrink the size of the laser beam to fit the 1.2×1.2mm area of the MEMS mirror plate.

Fig. 1. Schematic diagram of our experimental setup. FPGA: Field Programmable Gate Array. PMT: photomultiplier tube.

The reflecting area of the MEMS mirror is a silicon plate suspended by two torsional springs. Gimbal mounting of the mirror plate is used and the reflectivity of the mirror plate is enhanced by a thin layer of aluminum. For high transmission of the incident and reflected laser beam, the glass window covering on the MEMS mirror is anti-reflection coated around the wavelength of 1250nm.

After the MEMS mirror, we placed the designed miniaturizing tube-lens set. The scanned laser beam was imaged onto the back aperture of the objective and focused on the sample by a 60× water-immersion objective (NA=0.9) with 3mm effective focal length. The sample under test is placed on the slide. As the sample moved to the focal plane, the generated two-photon-excited fluorescence (TPEF) or second harmonic generation (SHG) signals were collected by a condenser and detected by a thermal electric (TE)-cooled PMT tube. The detected analog voltage signals were sampled by a data acquisition card with an 8.33MHz sampling rate synchronous with the FPGA system. Within each frame period, the acquired

#91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008

(C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10503

data vector will be reconstructed into a 512×512-pixel image according to the method described above. Thus reconstructed image or movie will be displayed and saved on the computer.

4. Two-photon fluorescence and second harmonic generation images

We first tested our TPEF image quality by the fluorescent beads (λ=625~640nm) with a 15-μm diameter. These beads were drop on the slide with a cover glass. As shown in the Fig. 2,

the 512×512-pixel image has a 76μm×70μm field of view. All the fluorescent beads appear with a shape close to a sphere. There is no shape distortion on the boundary of the image.

Fig. 2. Two-photon-excited fluorescent microscopic imaging of 15-μm fluorescent beads.

Then we used 1-μm fluorescent beads to test the transverse resolution of our imaging system. The solution of fluorescent beads was dropped on the slide and we took images on the fixed beads at the solution-glass interface. Figure 3(a) shows the TPEF image of two fluorescent beads close to the boundary of the image with a magnified field of view. To

improve the signal-to-noise ratio for this study, we first obtained a 512×512-pixel image by averaging 12 frames of images (corresponding to a 0.5-second integration time). We further

reduce the size of the image to 256×256 pixel by averaging every 4 pixels from the 512×512-pixel image. Taking a cross section along a line from A to A’, the corresponding full width of half maximum (FWHM) of the intensity profile is 1.33 μm (See Fig. 3(b)). Since the size of the fluorescent beads are close to the focused spot size, there is a plateau region around the maximum of the convolved trace. Considering the 2D convolution of a Gaussian point spread function (1-μm spot diameter) with a 1-μm fluorescent bead (a hat function with 1-μm diameter), the FWHM of the cross sectional trace is 1.35 μm. With a smaller FWHM, our result indicated a submicron transverse resolution of the studied imaging system.

#91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008

(C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10504

33 34 35 36 37 38 39

0.0

0.2

0.4

0.6

0.8

1.0

A'

Nor

mal

ized

Sig

nal (

A.U

.)

Length (μm)

(b)

A

Fig. 3. (a) Two-photon-excited fluorescence image of 1-μm fluorescent beads. (b) Intensity distribution of a fluorescent bead along a line crossing the peak intensity in Fig. 3(a).

After studying the spatial resolution performance, we examined the temporal capability of our MEMS-based miniaturized nonlinear microscope system. In order to test the frame-rate of our system, we recorded the Brownian motion of these 1-μm fluorescent beads suspended

in the solution. Figure 4 shows the recorded movie with a 24Hz frame rate and 512×512-

pixel images. The corresponding field of view is 76μm×70μm.

Fig. 4. (2.15 MB) The two-photon-excited fluorescence movie showing the Brownian motion of the 1-μm fluorescent beads. (10.5 MB version). These images were taken with a

24Hz frame rate and 512×512-pixel resolution. Image size:

76μm×70μm

Finally, this miniaturized system was also be applied to the second harmonic generation microscopy. Figure 5 shows a SHG microscopic imaging taken inside a frozen bovine tendon with the constructed microscopic system. This specific image was also taken by averaging 12 frames, corresponding to a 0.5-second integration time. With a sub-micrometer transverse resolution, the wavy type-I collagen fibers can be clearly identified in the sectioned SHG image [9-11].

(a)

#91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008

(C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10505

Fig. 5. Second harmonic generation image of a bovine tendon.

5. Summary

In summary, we demonstrate a high frame-rate (24Hz) miniaturized TPEF/SHG microscope system. This was achieved by asynchronous scanning of a MEMS mirror with a 9.8KHz resonant frequency. With a careful design on the radius of curvature of two miniaturized tube lenses, no image distortion was found on the boundary of the acquired 2D image and the corresponding transverse resolution can be down to sub-micron, through a regular high NA microscope objective.

Acknowledgments

This project is sponsored by the National Health Research Institute of Taiwan under NHRI-EX97-9201EI, the National Science Council of Taiwan under grant numbers of NSC96-2120-M-002-014 and NSC 96-2628-E-002-043-MY3, Program for Frontier and Innovative Research National Taiwan University under 95R0110, and by the National Taiwan University Research Center for Medical Excellence.

#91739 - $15.00 USD Received 15 Jan 2008; revised 19 May 2008; accepted 21 May 2008; published 30 Jun 2008

(C) 2008 OSA 7 July 2008 / Vol. 16, No. 14 / OPTICS EXPRESS 10506

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Optics Express

● Hengsheng Tang, Yigang Li, Yanwu Zhang, Yingfeng Li,

Hao Li, Xin Tu, Xiang Wu, Liying Liu, and Lei Xu

● pp. 9844-9849 [full text: PDF (492 KB)]

Materials

Cascaded wavelength conversion as favorable application

of nonlinear optical polymers

● Min-su Kim, Jung Jin Ju, Seung Koo Park, Jung Yun Do,

and Myung-Hyun Lee

● pp. 9726-9738 [full text: PDF (833 KB)]

Medical optics and biotechnology

Targeted transfection of stem cells with sub-20

femtosecond laser pulses

● Aisada Uchugonova, Karsten König, Rainer Bueckle,

Andreas Isemann, and Gabriel Tempea

● pp. 9357-9364 [full text: PDF (2346 KB)]

Enzymatic degradation of human skin dermis revealed by

fluorescence and reflectance spectroscopy

● Ye Yuan and Patricia Relue

● pp. 9857-9868 [full text: PDF (244 KB)]

http://www.opticsexpress.org/Issue.cfm (10 of 21) [6/30/2008 10:14:40 AM]

Optics Express

In vivo nanosecond laser axotomy: cavitation dynamics

and vesicle transport

● G. Nageswara Rao, Sucheta S. Kulkarni, Sandhya P.

Koushika, and Kaustubh R. Rau

● pp. 9884-9894 [full text: PDF (4376 KB)]

Polarization-sensitive reflectance imaging in skeletal

muscle

● Xin Li, Janaka C. Ranasinghesagara, and Gang Yao

● pp. 9927-9935 [full text: PDF (307 KB)]

Miniaturized probe for femtosecond laser microsurgery and

two-photon imaging

● Christopher L. Hoy, Nicholas J. Durr, Pengyuan Chen,

Wibool Piyawattanametha, Hyejun Ra, Olav Solgaard, and

Adela Ben-Yakar

● pp. 9996-10005 [full text: PDF (1216 KB)]

Metamaterials

Numerical determination of frequency behavior in cloaking

structures based on L-C distributed networks with TLM

method

http://www.opticsexpress.org/Issue.cfm (11 of 21) [6/30/2008 10:14:40 AM]

Optics Express

● Cèdric Blanchard, Jorge Portí, Juan-Antonio Morente,

Alfonso Salinas, and Bae-Ian Wu

● pp. 9344-9350 [full text: PDF (378 KB)]

Planoconcave lens by negative refraction of stacked

subwavelength hole arrays

● M. Beruete, M. Navarro-Cía, M. Sorolla, and I. Campillo

● pp. 9677-9683 [full text: PDF (1336 KB)]

Dual-band planar electric metamaterial in the terahertz

regime

● Yu Yuan, Christopher Bingham, Talmage Tyler, Sabarni

Palit, Thomas H. Hand, Willie J. Padilla, David R. Smith,

Nan Marie Jokerst, and Steven A. Cummer

● pp. 9746-9752 [full text: PDF (875 KB)]

Microscopy

Widefield subsurface microscopy of integrated circuits

● Fatih Hakan Köklü, Justin I. Quesnel, Anthony N.

Vamivakas, Stephen B. Ippolito, Bennett B. Goldberg, and

M. Selim Ünlü

● pp. 9501-9506 [full text: PDF (407 KB)]

http://www.opticsexpress.org/Issue.cfm (12 of 21) [6/30/2008 10:14:40 AM]

Optics Express

Cell tracking and detection of molecular expression in live

cells using lipid-enclosed CdSe quantum dots as contrast

agents for epi-third harmonic generation microscopy

● Chieh-Feng Chang, Chao-Yu Chen, Fu-Hsiung Chang, Shih-

Peng Tai, Cheng-Ying Chen, Che-Hang Yu, Yi-Bing Tseng,

Tsung-Han Tsai, I-Shuo Liu, Wei-Fang Su, and Chi-Kuang

Sun

● pp. 9534-9548 [full text: PDF (3809 KB)]

The phase-response effect of size-dependent optical

enhancement in a single nanoparticle

● Chen-Han Huang, Hsing-Ying Lin, Cheng-Hsiang Lin,

Hsiang-Chen Chui, Yun-Chiang Lan, and Shi-Wei Chu

● pp. 9580-9586 [full text: PDF (522 KB)]

STED microscopy with a supercontinuum laser source

● Dominik Wildanger, Eva Rittweger, Lars Kastrup, and

Stefan W. Hell

● pp. 9614-9621 [full text: PDF (4531 KB)]

Optical microscopic observation of fluorescence enhanced

by grating-coupled surface plasmon resonance

● Keiko Tawa, Hironobu Hori, Kenji Kintaka, Kazuyuki

Kiyosue, Yoshiro Tatsu, and Junji Nishii

● pp. 9781-9790 [full text: PDF (232 KB)]

http://www.opticsexpress.org/Issue.cfm (13 of 21) [6/30/2008 10:14:40 AM]

Optics Express

Tight focusing of laser beams in a λ/2-microcavity

● Dmitry Khoptyar, Raphael Gutbrod, Anna Chizhik, Jörg

Enderlein, Frank Schleifenbaum, Mathias Steiner, and

Alfred J. Meixner

● pp. 9907-9917 [full text: PDF (1326 KB)]

Individually-addressable flip-chip AlInGaN micropixelated

light emitting diode arrays with high continuous and

nanosecond output power

● H. X. Zhang, D. Massoubre, J. McKendry, Z. Gong, B.

Guilhabert, C. Griffin, E. Gu, P. E. Jessop, J. M. Girkin, and

M. D. Dawson

● pp. 9918-9926 [full text: PDF (253 KB)]

Nonlinear optics

Soliton switching and multi-frequency generation in a

nonlinear photonic crystal fiber coupler

● Kaisar R. Khan, Thomas X. Wu, Demetrios N.

Christodoulides, and George I. Stegeman

● pp. 9417-9428 [full text: PDF (250 KB)]

http://www.opticsexpress.org/Issue.cfm (14 of 21) [6/30/2008 10:14:40 AM]

Optics Express

Electronic control of soliton power transfer in silicon

nanocrystal waveguides

● Mengdi Li, Sergey A. Ponomarenko, Montasir Qasymeh,

and Michael Cada

● pp. 9587-9594 [full text: PDF (272 KB)]

Dispersive pulse compression in hollow-core photonic

bandgap fibers

● J. Laegsgaard and P. J. Roberts

● pp. 9628-9644 [full text: PDF (1845 KB)]

Substantial gain enhancement for optical parametric

amplification and oscillation in two-dimensional χ(2)

nonlinear photonic crystals

● Hsi-Chun Liu and A. H. Kung

● pp. 9714-9725 [full text: PDF (307 KB)]

Electrical control of parametric processes in silicon

waveguides

● Kevin K. Tsia, Sasan Fathpour, and Bahram Jalali

● pp. 9838-9843 [full text: PDF (269 KB)]

http://www.opticsexpress.org/Issue.cfm (15 of 21) [6/30/2008 10:14:40 AM]

Optics Express

SHG phase matching in GaSe and mixed GaSe11-xSx,

x0.412, crystals at room temperature

● Hong-Zhi Zhang, Zhi-Hui Kang, Yun Jiang, Jin-Yue Gao,

Feng-Guang Wu, Zhi-Shu Feng, Yury M. Andreev, Grigory

V. Lanskii, Aleksander N. Morozov, Elena I. Sachkova, and

Sergei Y. Sarkisov

● pp. 9951-9957 [full text: PDF (1137 KB)]

SHG in doped GaSe:In crystals

● Zhi-Shu Feng, Zhi-Hui Kang, Feng-Guang Wu, Jin-Yue

Gao, Yun Jiang, Hong-Zhi Zhang, Yury M. Andreev, Grigory

V. Lanskii, Viktor V. Atuchin, and Tatyana A. Gavrilova

● pp. 9978-9985 [full text: PDF (919 KB)]

Optical data storage

Multi-bits coding by multi-directional valley pits permitting

stamper mass-production and remote direction readout by

polarization reflection

● Toshihide Tsuru and Masaki Yamamoto

● pp. 9622-9627 [full text: PDF (669 KB)]

Optical devices

Colloidal ZnO quantum dots in ultraviolet pillar

microcavities

http://www.opticsexpress.org/Issue.cfm (16 of 21) [6/30/2008 10:14:40 AM]

Optics Express

● Tim Thomay, Tobias Hanke, Martin Tomas, Florian Sotier,

Katja Beha, Vanessa Knittel, Matthias Kahl, Kelly M.

Whitaker, Daniel R. Gamelin, Alfred Leitenstorfer, and

Rudolf Bratschitsch

● pp. 9791-9794 [full text: PDF (443 KB)]

Optical materials

Light propagation in dry and wet softwood

● Alwin Kienle, Cosimo D'Andrea, Florian Foschum, Paola

Taroni, and Antonio Pifferi

● pp. 9895-9906 [full text: PDF (118 KB)]

Optical trapping and manipulation

Theory of dielectric micro-sphere dynamics in a dual-beam

optical trap

● M. Kawano, J. T. Blakely, R. Gordon, and D. Sinton

● pp. 9306-9317 [full text: PDF (808 KB)]

Optics at surfaces

Complex propagation constants of surface plasmon

polariton rectangular waveguide by method of lines

● Tran T. Minh, Kazuo Tanaka, and Masahiro Tanaka

● pp. 9378-9390 [full text: PDF (470 KB)]

http://www.opticsexpress.org/Issue.cfm (17 of 21) [6/30/2008 10:14:40 AM]

Optics Express

Engineering the dielectric function of plasmonic lattices

● Amit Agrawal, Z. V. Vardeny, and Ajay Nahata

● pp. 9601-9613 [full text: PDF (251 KB)]

Numerical investigation of quasi-coplanar plasmonic

waveguide-based photonic components

● Jiwon Lee and Jaeyoun Kim

● pp. 9691-9700 [full text: PDF (927 KB)]

Surface plasmon microcavity for resonant transmission

through a slit in a gold film

● Qiao Min and Reuven Gordon

● pp. 9708-9713 [full text: PDF (187 KB)]

Optoelectronics

High speed hybrid silicon evanescent electroabsorption

modulator

● Ying-hao Kuo, Hui-Wen Chen, and John E. Bowers

● pp. 9936-9941 [full text: PDF (930 KB)]

http://www.opticsexpress.org/Issue.cfm (18 of 21) [6/30/2008 10:14:40 AM]

Optics Express

Photonic crystal fibers

Strategies for realizing photonic crystal fiber bandpass

filters

● S. K. Varshney, K. Saitoh, N. Saitoh, Y. Tsuchida, M.

Koshiba, and R. K. Sinha

● pp. 9459-9467 [full text: PDF (721 KB)]

Sensitivity of photonic crystal fiber modes to temperature,

strain and external refractive index

● Chengkun Chen, Albane Laronche, Géraud Bouwmans,

Laurent Bigot, Yves Quiquempois, and Jacques Albert

● pp. 9645-9653 [full text: PDF (486 KB)]

Supercontinuum generation in a water-core photonic

crystal fiber

● Alexandre Bozolan, Christiano J. de Matos, Cristiano M. B.

Cordeiro, Eliane M. dos Santos, and John Travers

● pp. 9671-9676 [full text: PDF (139 KB)]

Photonic crystals

Controlled sub-nanometer tuning of photonic crystal

http://www.opticsexpress.org/Issue.cfm (19 of 21) [6/30/2008 10:14:40 AM]

Optics Express

resonator by carbonaceous nano-dots

● Min-Kyo Seo, Hong-Gyu Park, Jin-Kyu Yang, Ju-Young Kim,

Se-Heon Kim, and Yong-Hee Lee

● pp. 9829-9837 [full text: PDF (3865 KB)]

Physical optics

The Poynting vector and angular momentum of Airy beams

● H. I. Sztul and R. R. Alfano

● pp. 9411-9416 [full text: PDF (644 KB)]

Transfer of orbital angular momentum from a super-

continuum, white-light beam

● Amanda J. Wright, John M. Girkin, Graham M. Gibson,

Jonathan Leach, and Miles J. Padgett

● pp. 9495-9500 [full text: PDF (400 KB)]

Quantum optics

Experimental demonstration of frequency-degenerate

bright EPR beams with a self-phase-locked OPO

● G. Keller, V. D'Auria, N. Treps, T. Coudreau, J. Laurat, and

C. Fabre

● pp. 9351-9356 [full text: PDF (174 KB)]

http://www.opticsexpress.org/Issue.cfm (20 of 21) [6/30/2008 10:14:40 AM]

Optics Express

http://www.opticsexpress.org/Issue.cfm (21 of 21) [6/30/2008 10:14:40 AM]