thomas f krauss university of st. andrews, supa, school of ... · “room-temperature emission at...

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TF Krauss, Pavia March 2012 No.1/60

Thomas F Krauss

University of St. Andrews, SUPA, School of Physics and Astronomy, St Andrews, UK

Integrated Nanophotonics: Issues and opportunities

Key collaborators: Pavia & Catania, Italy

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TF Krauss, Pavia March 2012 No.2/60

St Andrews

Scotland’s First University

Thomas F Krauss

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TF Krauss, Pavia March 2012 No.3/60

!  Scotland, UK !  18,000 people (1/3 students) !  80km from Edinburgh !  600 km from London

Glasgow Edinburgh

St Andrews Dundee

Aberdeen

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TF Krauss, Pavia March 2012 No.4/60

St Andrews. The home of golf

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TF Krauss, Pavia March 2012 No.5/60

LEO 1530 SEM/ Raith Elphy Plus!

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TF Krauss, Pavia March 2012 No.6/60 CAIBE machine!

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TF Krauss, Pavia March 2012 No.7/60

Photonic crystal waveguides

220 nm Si waveguide, airbridge or oxide clad epixnet nanostructuring platform: www.nanophotonics.eu

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TF Krauss, Pavia March 2012 No.8/60

Silicon Photonics

What’s the problem silicon photonics is trying to solve ?

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TF Krauss, Pavia March 2012 No.9/60

55 W-hour battery stores the energy of

1/2 a stick of dynamite.

If battery short-circuits, catastrophe is possible ...

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TF Krauss, Pavia March 2012 No.10/60

fJ fJ pJ

Optical interconnects save energy

fJ fJ fJ ?

Optical Interconnect

Electrical Interconnect

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TF Krauss, Pavia March 2012 No.11/60

On-chip Optical Interconnects

Use the photonics layer to shift data in a multicore architecture

Peter Kogge, DARPA study on Exascale Computing

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TF Krauss, Pavia March 2012 No.12/60

Peter Kogge, DARPA study on Exascale Computing

Possible monolithic realisation

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TF Krauss, Pavia March 2012 No.14/60

Optical interconnects

INTEL IBM

The idea is to use optical signals to distribute information on-chip, between processors.

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TF Krauss, Pavia March 2012 No.15/60

fJ fJ pJ

fJ fJ fJ

Optical interconnects save energy

Optical Interconnect

Electrical Interconnect

External lightsource + modulator

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TF Krauss, Pavia March 2012 No.16/60

External Lightsource + Modulator

!"

Requirements: Fast (ideally ps) => Carrier modulation =>Typical #n!10-4

=>Typical length ! cm

!" = !

k0!nL = ! # L = "2!n

$ 104"

Intel

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TF Krauss, Pavia March 2012 No.18/60

Solution: Resonant enhancement. Effective optical path maintained. Electrical path reduced.

++ +

+

+ - - - - -

Volume of active carriers reduced.

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TF Krauss, Pavia March 2012 No.19/60

Solution: Resonant enhancement. Effective optical path maintained. Electrical path reduced.

++

- -

Volume of active carriers reduced

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TF Krauss, Pavia March 2012 No.20/60

Kotura ring: 30"m dia. = 100"m circumf. 50 fJ/bit 10 GHz bandwidth Tuning energy: > 100 fJ/bit Tolerances ?

OpEx 17, 22484 (2009)

State-of-the-Art

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TF Krauss, Pavia March 2012 No.21/60

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TF Krauss, Pavia March 2012 No.22/60

fJ fJ pJ

fJ fJ fJ

Optical interconnects save energy

Optical

Electrical

+ #$"

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TF Krauss, Pavia March 2012 No.23/60

Photonic crystal waveguides

220 nm Si waveguide, airbridge or oxide clad

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TF Krauss, Pavia March 2012 No.24/60

Slow Light Mechanism!

a!

In the slow light regime, one can imagine the mode taking a longer route - that’s why it takes more time, and why there is more light inside the structure.!

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TF Krauss, Pavia March 2012 No.25/60

PhC MZI modulator

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TF Krauss, Pavia March 2012 No.26/60

Thermally activated Mach-Zehnder

80 "m long PhC

L. O'Faolain et al., IEEE Photonics Journal 2, 404 (2010)

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TF Krauss, Pavia March 2012 No.27/60

Dispersion curve

Switching performance

PhC – MZI Performance

L. O'Faolain et al., IEEE Photonics Journal 2, 404 (2010)

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TF Krauss, Pavia March 2012 No.28/60

n i p

Electrical operation. Work in progress…..

Electrical operation

William Whelan-Curtin Kapil Debnath

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TF Krauss, Pavia March 2012 No.29/60

Conclusion modulator

The slow light concept allows us to make small footprint, low driving power modulators with high bandwidth. They are of similar size, and therefore capacitance, as State-of-the-Art microring resonators, but offer far more bandwidth and do not need to be tuned.

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TF Krauss, Pavia March 2012 No.30/60

fJ fJ pJ

fJ fJ fJ

2. Solution: Internal lightsource

Optical Interconnect

Electrical Interconnect

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TF Krauss, Pavia March 2012 No.31/60

Defect luminescence

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TF Krauss, Pavia March 2012 No.32/60

PL from SOITEC wafer

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TF Krauss, Pavia March 2012 No.33/60

PL from SOITEC wafer + PhC Cavity

“Room-temperature emission at telecom wavelengths from silicon photonic crystal nanocavities”, R. Lo Savio et al., Appl. Phys. Lett. 2011

300x

300x enhancement !! Why 300x ? a)  Purcell effect b)  Extraction

efficiency

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TF Krauss, Pavia March 2012 No.34/60

Nature News & Views, 1997

FP =3!3

4" 2QV

!rad =" nonrad

" radFP

+" nonrad

E. M. Purcell, Phys. Rev. 69, 37 (1946).

Purcell effect

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TF Krauss, Pavia March 2012 No.35/60

Ti! f =2!h

f |H ' | i2"

Fermi’s Golden Rule

Matrix element Density of states

The Purcell factor relates to Fermi’s Golden Rule The transition between two quantum mechanical states is given by the product of the matrix element (derived from the Hamiltonian) and the density of final states. This transition probability is also called decay probability and is related to mean lifetime.

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TF Krauss, Pavia March 2012 No.36/60

%,!"FP =

3!3

4" 2QV

Ti! f =2!h

f |H ' | i2"

%,!"

i

f

To enhance the interaction between a cavity and an emitter, they need to agree in emission wavelength and be in the same space -> Q/V

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TF Krauss, Pavia March 2012 No.37/60

Fp =!

"cavity

"membrane

!cavity = 0.9

!membrane = 0.036

! = 300

Fp =12, !ext = 25

Extraction efficiency

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TF Krauss, Pavia March 2012 No.38/60

The Purcell-factor makes defect emission “Room-temperatureable”

!rad =" nonrad

" radFP

+" nonrad

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TF Krauss, Pavia March 2012 No.39/60

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TF Krauss, Pavia March 2012 No.40/60

Using hydrogen treatment and well-designed designed photonic crystal cavities, we can achieve significant light emission directly from silicon. This is not yet sufficient for optical interconnects, but further improvements are possible. The output power is competitive with comparable III-V devices,. although not with III-V materials as such.

Conclusion light sources

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TF Krauss, Pavia March 2012 No.41/60

2. Silicon Nanophotonics for Biosensors

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TF Krauss, Pavia March 2012 No.42/60

The Lab on a chip (LoC) concept aims to realise biochemical analysis/synthesis in a miniaturised format.

Lab on a chip (LoC)

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TF Krauss, Pavia March 2012 No.43/60

Surface Plasmon sensor!

Very high sensitivity -> Biacore Broad resonance

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TF Krauss, Pavia March 2012 No.44/60

Silicon ring resonator as biodetector!

K. deVos, R. Baets et al., OPTICS EXPRESS 15, pp. 7610-7615 (2007).!

Lower sensitivity Narrow resonance -> Genalyte

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#$"%&"

High sensitivity Narrow resonance -> ???

Di Falco, Krauss et al., APL 2009

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Genalyte

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TF Krauss, Pavia March 2012 No.47/60

Light source Spectrum Analyser

Chip in a lab

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TF Krauss, Pavia March 2012 No.48/60

The possible integration of silicon light sources would lead to miniaturisation, large scale integration and simplicity.

Source

Transducer

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TF Krauss, Pavia March 2012 No.49/60

Light source Spectrum Analyser

Lab on a chip

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TF Krauss, Pavia March 2012 No.50/60

Autonomous sensors

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TF Krauss, Pavia March 2012 No.51/60

2nd problem: Diffusion time

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TF Krauss, Pavia March 2012 No.52/60

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TF Krauss, Pavia March 2012 No.53/60

H Schmidt & AR Hawkins, Nature Photonics August 2011

Optofluidic laser

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TF Krauss, Pavia March 2012 No.54/60

H Schmidt & AR Hawkins, Microfluidics & Nanofluidics (2008)

Fluorescence correlation spectroscopy (FCS), FRET,… Measure changes caused by molecular binding, not using the surface.

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TF Krauss, Pavia March 2012 No.55/60

As it does not have volume, only surface, its entire structure is exposed to its environment and responds to any molecule that touches it. This makes it a good material for super-sensors capable of detecting single molecules of toxic gases.

Graphene

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TF Krauss, Pavia March 2012 No.56/60

Key issues Biology 1. Lab on a chip – chip on a lab: Integration.

2. Move away from surface affinity biosensor. Novel integrated sensor architectures.