Post on 03-Sep-2020
Professor Benjamin J. EggletonCUDOS Director ARC Federation FellowSchool of Physics, University of Sydneywww.physics.usyd.edu.au/cudosegg@physics.usyd.edu.au
The Semaphore:An Example from History
Light travels well through fibre
• High-refractive index core with low-index background
• Light stays in core by total internal reflection
(b)n n21
θ
θ
θ
θ1
1
1
2
θ1
(a)
8.3 m
125 mμ
μ
cladding
core
Too much is not enough!
was being
Light propagation through atmosphere
• Light scatters when it travels through the atmosphere
• Range limited to a few kilometers
From: http://www.cablefree.co.uk/
Examples from history: Internet and Cellular Network
eTeaching
eHealth
Bandwidth demand!
What is CUDOS doing?
Motivation / Context–optical regeneration
• In optical communication networks, signal distortion occurs due to: Spontaneous emission in optical amplifiers, cross-talk, dispersion, nonlinearities, polarization effects…
• Requires regeneration– Electronic bottleneck
at 40Gb/s– All-optical to replace
electronic
Input Power
Output Power
Time
Input Power
Time
Output Power
Using the Success of Electronics: Microfabrication
Ultra Small, Ultra Fast
Ultra Small, Ultra Fast
Context and Outcomes
2 metres The present
The futureBits/s
The Photonic Chip
Fibre to chip coupler
Wavelength demuxJunctions
Wavelength converterWaveguides and bends
Signal regeneration
Delay lines
Optical switch
Introduction: Basic parameters
Bragg condition
Ln
Position
Δn
Λ= nB 2λ
At λB and close to it: Bragg reflection due to PBGFurther from λB: dispersion
Bragg reflection occurs for range of wavelengths:
10 cm long grating
Evan
esce
nt
nn // Δ≈Δ λλ
Natural
2D Photonic CrystalMicrostructured
Optical Fibre
3DPhotonicCrystal
2D Photonic CrystalPlanar Waveguids
1D Photonic Crystal (Bragg grating and thin film stack)
Photonic crystals
1. Breakthrough technology
Ultra-tight confinement
Ultra-dispersion
Δλ = 1% ~ 50°
10μm
Photonic Crystal: Ultra-compact & ultra-control
Ultra-nonlinearity
2D slab SOI structure fabricated at IBM on a 8-inch CMOS line - "S. McNab and Y.Vlasov, IBM Watson".
Chalcogenide Chalcogenide waveguide waveguide with small with small bend radiusbend radius
Bragg Bragg gratinggrating
cmcm’’ss
InIn
OutOut
YY--junctionjunction
Optical Optical fibrefibre
Inverse Inverse taper taper couplercoupler
Photonic chip all-optical regenerator
Photonic Chip-2R optical regenerator
Silicon Wafer
Silica
As2S3
Polymer W
hH
Ta’eed et al. Opt. Lett 2005.
First embodiment of photonic chip all-optical processor
CUDOS device test-bed
160Gb/s Bit-Error-Rate System
(Dr Martin Rochette, Canadian Research Fellowship)
CUDOS photonic crystaloptical switch
Ultra-compact, optical switch in nonlinear 2D PC
Photonic crystal fabricated in chalcogenide film
C. Grillet, C. Smith, D. Freeman, S. Madden, B. Luther-Davis, E.C. Magi, D.J. Moss, B.J. Eggleton, “Efficient coupling to chalcogenide glass photonic crystal waveguides via silica optical fiber nanowires,” Optics Express 14, 1070-1078 (February 2006)C. Grillet, D. Freeman, B Luther-Davies, S Madden, R McPhedran, D.J. Moss, M. J. Steel, B.J. Eggleton, “Characterization and modeling of Fano resonances in chalcogenide photonic crystal membranes,” Optics Express 14, 369-376 (January 2006).
Hard to couple light into a PCWG
• Mode shape/size mismatch
• vg / neff mismatch
Coupling light into PCWGand how to probe these structures?
Optical fiber
Photonic crystal microcavityPhotonic crystal waveguide
2D PC slab
Evanescent coupling
Evanescent coupling between tapered fiber and a PCWG or passive resonator
• Versatile approach (coupling to waveguides, cavities…)• Efficiency > 95% experimentally demonstrated• Bandwidth ~ 20nm @ 1600nm
Silica optical nanowires
• Spliced Optical fibre tapered using standard flame brushing method (Birks & Lee, Vol. 10 JLT 1992)
• Fibre dimensions reduced by up to 500 timesFibre
Butane flame
Evanescent coupling to chalcogenidePC waveguides using silica nanowires
a)
b)
c)110 μm
300 μm
90 μm
Silica nanowires
Excitation of PC mode
100 μm