2572-1
Winter College on Optics: Fundamentals of Photonics - Theory, Devices and Applications
10 - 21 February 2014
Waveguide theory (and photonic circuit design)
A. Melloni Dip. Elettronica, Informazione e Bioingegneria Politecnico di Milano Italy
Winter College on Optics: Fundamentals of Photonics Theory, Devices and Applications Waveguide theory (and photonic circuit design)
A. Melloni Dip. Elettronica, Informazione e Bioingegneria Politecnico di Milano, Italy
7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators –A. Melloni, Politecnico di Milano Waveguide theory and photonic circuit design
- Waveguides (no theory…) - The role of index contrast in waveguides (survey of technologies, type of waveguides, index contrast…) - Bends and advanced topics on bends (the matched bend,...) - The dark side of integrated optical waveguides (backscatter, xtalk, losses, spurious modes, the (ng-neff) role….) - An excursus on ring resonators: history, spectral characteristics, applications, ... - Circuits: MZ, rings, higher order filters, delay lines, … - The circuit approach (building Blocks, Circuit simulators and few slides on Aspic, our circuit simulator that will be used at the end of the course for hands-on session). - The structure of generic foundries and available generic foundries
7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators –A. Melloni, Politecnico di Milano WAVEGUIDES
Cover
CORE
Substrate
ICTP Winter School, Trieste, 2014 A. Melloni WAVEGUIDES
n2 > n1
n1 Impedance
ICTP Winter School, Trieste, 2014 A. Melloni WAVEGUIDES
Ray Optics (forget…)
Electromagnetic Theory (Maxwell Equations) - rigorous - (Jiri Ctyroky, next week)
ICTP Winter School, Trieste, 2014 A. Melloni WAVEGUIDES
Radiative modes Guided modes (plane waves)
Dielectric waveguides are between free space and metallic waveguides
ICTP Winter School, Trieste, 2014 A. Melloni Characteristics of the modes
Guided modes are - orthogonal (in space and in time) -do not exchange power - z independent (do not change the shape) - solution of the wave equation - Propagate as exp(-jz) - Attenuate as exp (-z)
- Each mode has his , , ng… - Depend on the cross section - Have a cutoff wavelength (if asymmetric) -… ICTP Winter School, Trieste, 2014 A. Melloni Existing modes and Excited modes
waveguide
Fiber, laser, …
ICTP Winter School, Trieste, 2014 A. Melloni Existing modes and Excited modes
waveguide
Fiber, laser, …
ICTP Winter School, Trieste, 2014 A. Melloni Leaky modes
Leaky modes or quasi-mode are packets of radiative modes Behave as badly guided modes
Guided mode Leaky mode
ICTP Winter School, Trieste, 2014 A. Melloni WAVEGUIDES
ICTP Winter School, Trieste, 2014 A. Melloni WAVEGUIDES
ICTP Winter School, Trieste, 2014 A. Melloni Other Waveguides
Slot waveguide Photonic Crystal waveguide
Hollow waveguide
Segmented waveguide Good for sensing !
ICTP Winter School, Trieste, 2014 A. Melloni The characteristics of an Optical Waveguide
Single mode (why? …always?) Low loss (dB/cm?, dB/m?; fibers 0.2 dB/km !) Low (high) polarization dependence Small bending radius Large mode (for efficient fiber coupling) Active controls (thermooptic, electrooptic, carriers….) Nonlinearities ?
ICTP Winter School, Trieste, 2014 A. Melloni The characteristics of an Optical Waveguide
Mode shape
Phase constant Effective index
Group index
ICTP Winter School, Trieste, 2014 A. Melloni Dispersion diagram
ICTP Winter School, Trieste, 2014 A. Melloni Refractive index contrast
ICTP Winter School, Trieste, 2014 A. Melloni Technologies and Waveguides
Ge:SiO2 SiON Si3N4 InP As2S3 SOI n 0.5…3 % 2…8 % 38 % 3 / 70 % 60…100 % 140%
Mach-Zehnder D. Couplers, Y, MMI, Star couplers
Ring Resonators
Gratings
ICTP Winter School, Trieste, 2014 A. Melloni Index contrast vs size and NA
ICTP Winter School, Trieste, 2014 A. Melloni High or low index contrast?
ICTP Winter School, Trieste, 2014 A. Melloni Low index contrast: classical integrated optics
Weakly Guiding “integrated” optics
SiO2 doped Ge, B, P…, polymers n< 1% Waveguide dimensions 5x5 m
Rmin > 1 cm Low loss, < 0.1 dB/cm Excellent fiber waveguide coupling (<0.1dB) Low birefringence (10‐5)
Foundries available on the market Reliable and stable Very low integration scale Can be athermal
ICTP Winter School, Trieste, 2014 A. Melloni High index contrast glasses
Integrated optics
SiON (eventually doped Ge), polymers n< 3‐5 % (1.5….20 %) Waveguide dimensions 2x2 m (4%) 1.2x1.2 m (20%)
Rmin: 1 mm (4%) …. 30 m (20%) Moderate loss, 0.15‐0.5 dB/cm Fiber coupling need mode adapter (0.3 dB) Low birefringence (10‐5)
Foundries … a long story ! Non stoichiometric…., absorbs at 1510 (N‐H bound) Medium integration scale
ICTP Winter School, Trieste, 2014 A. Melloni Semiconductors: very high index contrast
ICTP Winter School, Trieste, 2014 A. Melloni Photonics Integration
Courtesy of TU/e
ICTP Winter School, Trieste, 2014 A. Melloni Photonic Integration ‐ reduction of volume and packaging cost
Compact fibre-based cross- Photonic Integrated cross- connect module 1997 connect chip 1998 4-channel 2x2 OXC 4-channel 2x2 OXC
Courtesy of Tu/e – Eindhoven University
ICTP Winter School, Trieste, 2014 A. Melloni Towards 1 Tbit/s Tx&Rx system on chip…
ICTP Winter School, Trieste, 2014 A. Melloni Why VLSI ?
Yield 1/(Chip Area * # defects per cm2)
“Cost” Chip Cost / # functions / Yield
70 % of the cost is in the package…
90% of the time goes in testing and validation…
ICTP Winter School, Trieste, 2014 A. Melloni Let’s bend the waveguide !
A straight waveguide….
… and a bent waveguide
ICTP Winter School, Trieste, 2014 A. Melloni Bends
ICTP Winter School, Trieste, 2014 A. Melloni Bending radius and FSR
Losses n4
‐1.5 Rmin 5n m (0.1 dB/rad)
FSR=c/(2 g)= Rn =29n-1.5 [nm]
ICTP Winter School, Trieste, 2014 A. Melloni Bent waveguide
n0(x,y)
R
ICTP Winter School, Trieste, 2014 A. Melloni Bent waveguide
Bending radius
ICTP Winter School, Trieste, 2014 A. Melloni Bend and straight modes
Bend mode=linear combination of straight modes Straight mode=linear combination of bend modes For monomode waveguide only 2 modes are sufficient
b a11 a22
+ =
Lossless Lossy b
Loss and distortion !
ICTP Winter School, Trieste, 2014 A. Melloni The matched bend R, 1 a1+b2 =1+….
If R=N beat lengths 1=a1+b2
2m 2 4 c2 1 2 12 Rmb 1 2
ICTP Winter School, Trieste, 2014 A. Melloni The matched bend
Matched bend Unmatched bend 50.0% 49.7% 42.7% 56.6%
Lithium Niobate waveguide, R=5 cm =0.5°
ICTP Winter School, Trieste, 2014 A. Melloni (Roughness induced) Backscatter
ICTP Winter School, Trieste, 2014 A. Melloni Waveguide surface…
Cross section shape Stress and strain Sidewall Roughness w Surface states Doping (1015) …….
-3 neff / w=2⋅10 w= 1nm =1nm = 1nm =1 dB/cm
ICTP Winter School, Trieste, 2014 A. Melloni Scattering processes in waveguides
Sidewall roughness w Scattering processes
αrad Coupling with radiation modes Coupling into T counter‐propagating modes x (BACKSCATTERING) R x n w Scattering w2, Δn2
Silicon wires: w ≈ 5 nm αtot = 10 dB/cm
ICTP Winter School, Trieste, 2014 A. Melloni Backscattering in silicon wires
Tx Roughness rms w< 2 nm Rx
w Lwg = 1 mm 0 single mode multi mode Backscattering gives a -10 TE [dB/mm] small contribution to
x -24 dB/mm -20 propagation loss
Rx ≈ 10% -30
-40 However… Lwg = 1 mm
Backscatterd R power -50 300 400 500 600 waveguide width w [nm] ICTP Winter School, Trieste, 2014 A. Melloni Backscattering in silicon wires
T x Roughness rms w< 2 nm Rx
w Lwg 0 single mode multi mode Tx reduces with Lwg -10 TE [dB/mm] Rx increase with Lwg x -20
Tx = Rx -30 Reflection equals -40 = 15 dB/cm = 2.5 dB/cm transmission after a wg 9 mm 58 mm length Lwg of only…
Backscatterd R power -50 300 400 500 600 waveguide width [nm] ICTP Winter School, Trieste, 2014 A. Melloni High vs low index contrast
Silicon (Δn = 140%) SiON (Δn = 4.5%) Si / SiON SiO2 h = 220 nm h = 2.2 μm h w = 2.2 μm w0 = 490 nm 0 w Si single mode multimode > 2 order of magnitude -20 Silicon (TE) higher than in [dB/mm]
x low n waveguides -30 25 dB -40
-50 SiON (TE) -60 Backscatterd R power 0.6 0.8 1 1.2 w / w0 ICTP Winter School, Trieste, 2014 A. Melloni High vs low index contrast
Silicon (Δn = 140%) SiON (Δn = 4.5%) h = 220 nm h = 2.2 μm Si / SiON w = 2.2 μm w0 = 490 nm 0 SiO2 h single mode multimode w Si -20 Silicon (TE) [dB/mm] x -30 Maximum waveguide -32 dB length for a given -40 backscattering level ?
-50 SiON (TE) -60 Backscatterd R power 0.6 0.8 1 1.2 w / w0
SOI WG SiON WG SiO2:Ge WG Optical fiber (Δn ≈ 140 %) (Δn ≈ 4.5 %) (Δn < 1 %) (Rayleigh)
ICTP Winter School,L =Trieste, 200 μ 2014mL =A. 7 Melloni cm L = 1 m L = ∞ What backscattering depends on?
Let’s find a golden rule Given a certain roughness w, backscattered power depends only on the square sensitivity S2
neff neff -20 Silicon (TE) S ng neff [dB/mm] w
x -30 S 2 model The S2 relation holds 25 dB -40 independently of size, shape, material and index contrast -50 SiON (TE) (Δn) -60 Backscatterd R power 0.6 0.8 1 1.2 w / w0 F. Morichetti et al., PRL 104, 033902 (2010) ICTP Winter School, Trieste, 2014 A. Melloni Also attenuation goes as ng--nneff
ICTP Winter School, Trieste, 2014 A. Melloni Attenuation and backscatter vs technology
ICTP Winter School, Trieste, 2014 A. Melloni Radiation mode Xtalk
g Pout Pxt WG1 Pin WG2
g < 2.5 m Indium phosfide technology -10 Power transfer due to evanescent mode coupling Pout -20 exp(2g) g 2 -30 35 dB e2 g -40 2.5 m g < 30 m
Power [dB] Xtalk due to radiation mode -50 coupling FMM Pxt 2 g WG2 -60 BPM (no roughness) -70 2 3 5 10 15 20 25 30 Gap [m]
ICTP Winter School, Trieste, 2014 A. Melloni An intuitive view of xtalk
WG1
Tx 1/g2 Rx
ICTP Winter School, Trieste, 2014 A. Melloni Minimize S to minimize backscatter
• Reduce the index contrast: SSOI=1.6e-3; SSiON=1e-5
• Use TM mode: in SOI STE=1.7e-3; STM=7e-4 ( > 15 dB)
• Use a suitable upper cladding: backscatter of SOI wg with Air -21dB/mm; -18dB/mm; 2 SU8 SiO -23dBmm • Engineer the waveguide cross section shape: silicon wire -21dB/mm; rib -39 dB/mm
ICTP Winter School, Trieste, 2014 A. Melloni Other ingredients
ICTP Winter School, Trieste, 2014 A. Melloni Directional coupler
0 W 3 L c
g S 1 2 L
ICTP Winter School, Trieste, 2014 A. Melloni Directional coupler
Typical Insertion Loss < 0.1 dB (0.03-0.06 dB)
Small gaps excite higher order modes
0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 -3 .0 -3 .0
-2 .5 gap=50nm gap=100nm -2 .5 -2 .0 -2 .0 -1 .5 Lπ=5.7µm -1 .5 Lπ=10.2µm -1 .0 -1 .0 -0 .5 -0 .5 0. 0 0. 0 0.5 0.5 1.0 1.0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 -3 . -3 .0 gap=150nm -3.0 gap=200nm -2 .5 -2 .5 -2.0 -2 .0 -1 .5 -1 .5 Lπ=16.3µm Lπ=25.5µm -1 .0 -1 .0 -0 .5 -0 .5 0.0 0.0 0.5 0.5 1.0 1. 0 5 . 5 ICTP Winter School, Trieste, 2014 A. Melloni Other splitter/combiners W 2 Y-Branch
S W 0 0 2N-1 1 L g N-1 N
L
MMI – Multimode Intertference Coupler
Star Coupler ICTP Winter School, Trieste, 2014 A. Melloni Power is nothing without control…
Au+NiCr+Ti
ICTP Winter School, Trieste, 2014 A. Melloni Thermal Control in SiON
SiON wg 7 m 10 m 9-15 m Heater 120 SiO 2 SiO2 100 up cladding low cladding 7-9 m 80 T [°C] 10 m 60
40 36°C Temperature Temperature
20 P = 300 mW (2mm) 0 Typical length 1-3 mm 0 5 10 15 20 Depth [ m] shift =300mW (100°C) -5 -1 neff / T=1.110 °C Response time: ~100s B < 210-5 /100°C
ICTP Winter School, Trieste, 2014 A. Melloni Thermal Control in SOI
-30
Thermo-optic efficiency -35
-40 Power consumption: 52 μW/GHz -45 0V 12.5 mW/GHz in SiON 1.0V 2.0V
Intensity [dB] - Intensity -50 3.0V 4.0V f=2B=200 GHz = 10 mW/ring 3.1 nm / 6V 5.0V -55 6.0V
-60 1549 1550 1551 1552 1553 Wavelength - [nm] Time response Thermal crosstalk
1 cold hot 7 m 0.8 = 4 μs ring ring tres = 12 μs 0.6 R R2 0.4 1 0.2
Optical intensity 28° 0.7° 0 -5 0 5 10 15 20 C =0.06C nm Time [us] =2.5 nm
ICTP Winter School, Trieste, 2014 A. Melloni Mach‐Zehnder interferometer (Filter)
It is a Finite Impulse Response filter, FIR DROP port: 1 zero THROUGH port: 1 zero (2 zeroes in the origin)
ICTP Winter School, Trieste, 2014 A. Melloni Mach‐Zehnder interferometer (Filter)
ICTP Winter School, Trieste, 2014 A. Melloni Mach‐Zehnder interferometer (Filter)
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonators = Fabry-Perot
K Lr/2
Lr R, K R, K K
It is an Infinite Impulse Response filter, IIR DROP port: 1 pole THROUGH port: 1 pole, 1 zero
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonators = Fabry-Perot
K Lr/2
Lr R, K R, K K
ICTP Winter School, Trieste, 2014 A. Melloni Ring Resonator Filter
r r z 1 jt2 1 2 H through (z) 1 Drop 1r1r2 z r2 ,Lr 1 t1t2 z jt H drop (z) 1 In 1 Through 1 r1r2 z
r jL 1 z e r
Resonance condition: L 2m , m 0,1,2,... r
Free Spectral Range: c FSR ng Lr
ICTP Winter School, Trieste, 2014 A. Melloni Ring Resonator Filter
Transmission Group Delay
t2=0.2 t2=0.2
Frequency/FSR Frequency/FSR
ICTP Winter School, Trieste, 2014 A. Melloni Phase shifter (all pass filter)
,Lr r e jLr T() jLr In jt Out 1re
r Resonance condition: 0 L 2m , m 0,1,2,... r
-1 Free Spectral Range: -2 c FSR -3 ng Lr Trasmission [dB] Trasmission 2 -4 t = 0.5, = 0 ... 0.75 dB
-5 1550 1550.1 1550.2 1550.3 1550.4 1550.5 critical coupling = r [nm] =1 lossless) ICTP Winter School, Trieste, 2014 A. Melloni Phase shifter (all pass filter)
Transmission Phase
Frequency/FSR Frequency/FSR
ICTP Winter School, Trieste, 2014 A. Melloni Effect of a refractive index perturbation
n due to Tolerances, Temperature, Birefringence, aging…
B
ICTP Winter School, Trieste, 2014 A. Melloni a lot of formulae….
ICTP Winter School, Trieste, 2014 A. Melloni Spectrum of backscattering
SiO α = 2 dB/cm T 2 In x 220 nm Si R SOI wg x 480 nm
Si WG length: 1 mm 0 (a) Tx -10
[dB] Backscatter is a random x white noise
, R -20 x
T in wavelength‐domain Rx -30
1546 1547 1548 1549 1550 1551 1552 Wavelength [nm] ICTP Winter School, Trieste, 2014 A. Melloni Backscattering in ring resonators
In α = 2 dB/cm Tx Reflection can even exceed Rx K transmission Spectral response distortions (notch splitting)
Lr K = 0.15
0 (a) Tx Rx > Tx -10 0 [dB] x Rx -10
, R -20 x T -20 -30 -30 1546 1547 1548 1549 1550 1551 1550 1550.5 1551 1551.5 Wavelength [nm] ICTP Winter School, Trieste, 2014 A. Melloni Backscattering in ring resonators
Where is the light ? In α = 2 dB/cm Tx Ring with Finesse ≈40 Rx K Waveguide attenuation 2.0 dB/cm (roundtrip losses=0.025dB)
Finesse * roundtrip loss = 1 dB Lr K = 0.15
0 (a) Tx Rx > Tx -10 0 [dB] x Rx -10
, R -20 x T -20 -30 -30 1546 1547 1548 1549 1550 1551 1550 1550.5 1551 1551.5 Wavelength [nm] ICTP Winter School, Trieste, 2014 A. Melloni Backscattering in ring resonators
250 experiment 2 2 200 ng model ng
150
100 light trapping originates 50 coherent backscattering
Backscattering enhancement Backscattering 0 0 20 40 60 80 100 Group index ng (Q factor, finesse…) F. Morichetti et al., APL 96, 081112 (2010)
ICTP Winter School, Trieste, 2014 A. Melloni An excursus on ring-resonators
history, properties and applications
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonator: the origin
E. A. J. Marcatili, “Bends in optical dielectric guides,” Bell Syst. Tech. J. 48,
Sept. 1969
P. Troughton, ”Measurement techniques in microstrips”, Elect. Letters, January 1969
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonators: the origin
M. Miyagi, “Design theory of high-Q optical ring resonator with asymmetric three-layered dielectrics”, Optical and Quantum Electronics, October 1978
(McGill University, Canada)
R. G. Walker and C.D.W. Wilkinson “Integrated optical ring resonators made by silver ion-exchange in glass”, Applied Optics, April 1983
GLASGOW UNIVERSITY
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonators: the origin
M. Miyagi, “Design theory of high-Q optical ring resonator with asymmetric three-layered dielectrics”, Optical and Quantum Electronics, October 1978
(McGill University, Canada)
R. G. Walker and C.D.W. Wilkinson “Integrated optical ring resonators made by silver ion-exchange in glass”, Applied Optics, April 1983 ~1000 BC GLASGOW UNIVERSITY ~2000 AD
ICTP Winter School, Trieste, 2014 A. Melloni Z-cut LiNbO3 Silicon Oxynitride A. Mahapatra, Applied Optics, De Brabander, PTL, May 1994 August 1985 m
AlGaAs/GaAs D. Rafizadeh, JLT 1998 The smallestring, R=2.2 InP, P. Absil, Univ. Maryland, 2001
ICTP Winter School, Trieste, 2014 A. Melloni Silicon on Insulator Indium Phosphide Ghent University Fraunhofer Institute 2003 2003
Polimer, A. Rabiei, ETH, 2003
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonators: a key building block
K. Bergman
IBM Optical Interconnects
INTOPSENS
Telecommunications BOOM-ICT Optical (bio)sensors
ICTP Winter School, Trieste, 2014 A. Melloni Ring resonators: a key building block
Cornell University, M. Lipson, 2009 Glasgow Univ. / PoliMi, 2011 2007 2012
ICTP Winter School, Trieste, 2014 A. Melloni To be continued….
Tomorrow, more rings more fun…!
Winter College on Optics: Fundamentals of Photonics Theory, Devices and Applications
ICTP Winter School, Trieste, 2014 A. Melloni from Ring to Rings…
CROW – Coupled Resonator Optical Waveguide
A. Yariv Caltech 1999 Microwave C. Madsen Bell Labs 1999 DSP R. Orta Politecnico Torino 1999 DSP A. Melloni Politecnico Milano 2002 Microwave V. Van Maryland Univ. 2006 Electronic/Microwave
ICTP Winter School, Trieste, 2014 A. Melloni Progress in tuneable ring-ring-CROWCROW
2009
2007
2008
2009
2010
ICTP Winter School, Trieste, 2014 A. Melloni A reconfigurable CROW
waveguide section: 480 nm x 220 nm Propagation loss: 0.9 – 1.5 dB/cm
buried in SiO2 1 m thick HSQ / SiO2 HSQ NiCr heaters
Each cavity can be addressed Si Negligible thermal cross-talk (Si) Response time: 4 s SiO2 Power consuption: 52 μW/GHz (10 mW @ 100Gb/s)
ICTP Winter School, Trieste, 2014 A. Melloni 8-rings Bandpass filters in SOI
Return loss: -15 dB; IL 0.5 dB; In-band ripple <0.2 dB; Off-band rejection >50 dB Intensity [dBm] Intensity
Wavelength [nm]
ICTP Winter School, Trieste, 2014 A. Melloni Tunable Delay lines
1 byte continuously tuneable delay at 10 and 100 Gbit/s demonstrated
OUT open rings closed rings
IN λr = λin λr ≠λin
F. Morichetti et al., Optics Express, Vol. 15, 25, December 2007 A. Canciamilla et al., Journal of Optics, IOP, 2010 A. Melloni et al., IEEE Photonics Journal, vol. 1, no. 4, 2010
ICTP Winter School, Trieste, 2014 A. Melloni Tuneable ringring--basedbasedCROW in SOI
B = 87 GHz 15 ps 0
M = 2 -2
-4 FSR = 450 GHz 30 ps
M = 4 -6
45 ps Transmission [dB] -8 1552 1553 1554 1555 1556 1557 1558 80 M = 6 60 2 Delay M 40 B 20 Delay [ps] Delay
= 7.5 ps/ring 0 1552 1553 1554 1555 1556 1557 1558 wavelength [nm] ICTP Winter School, Trieste, 2014 A. Melloni Data transmission at 10 Gbit/s
100 ps Intensity modulation OOK NRZ @ 10 Gbit/s
In
Reconfiguration -hitless Out - time 100 s -power 5 mW
ICTP Winter School, Trieste, 2014 A. Melloni Tuneable pulse delay @100Gbit/s
B = 87 GHz 10 ps In τ
Out
Fractional delay = 7.5 ps/RR 1 (0) Storage efficiency 0.8 89 ps (8 bits) 0.66 bit/RR 0.6 9 ps (4) Fractional loss 0.4 (8) ≈ 1.1 dB/bit (12) 0.2 11 ps Normalized intensity Normalized Pulse Broadening (1 byte) 0 ≈ 20% 0 20 40 60 80 100 120 Delay [ps] ICTP Winter School, Trieste, 2014 A. Melloni Tuning / Reconfiguration
R. De La Rue, Opt. Express 12, 2004 FLEXIBLE !! Each cavity can be addressed Power consuption: 30 mW/ Negligible thermal cross-talk (Si) 2 mW/nm Response time: 4 s Power consuption: 52 μW/GHz B Pulse spatial N p (20 mW @ 100Gb/s) extention cp Bcrow
ICTP Winter School, Trieste, 2014 A. Melloni resonators_1
(a) (b) (c)
(d) (e) (f)
(g) (h)
7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators –A. Melloni, Politecnico di Milano Other properties… Tolerances t 2 2 d t t t t d d=1 nm ‐‐> =100 GHz
Polarization conversion
Induced by bending, sidewall angle, asymmetry and roughness
Proportional to 1/R and Hybridness (Ez/Ex)
(stay away from low birefringence wg…)
ICTP Winter School, Trieste, 2014 A. Melloni The ingredients
ICTP Winter School, Trieste, 2014 A. Melloni Just a taste of nonlinearity
ICTP Winter School, Trieste, 2014 A. Melloni Nonlinear response (TPA and thermal)
Silicon (and InP) ring resonator 0 0.6
TPA FCA T -0.2 0.5
Si -0.4 0.4
-0.6 0.3 SiO2 -0.8 0.2 Extra-losses [dB] Resonance[nm] shift -20 +22 dBm -1 0.1
-25 -1.2 0 -30 -20 -10 0 10 20 30 Local Power - P [dBm] -35 loc
-40 Intensity [dB] Insertion loss -45
-50 ‐2 dBm Frequency shift
1549.8 1549.85 1549.9 1549.95 1550 1550.05 1550.1 Spectral distortion Wavelength [nm]
ICTP Winter School, Trieste, 2014 A. Melloni 93 Towards power insensitive operation
Si ring resonator PLOCAL = 25.5 dBm Polymer 0 Si -5
-10 SiO2 -15 300600 Standard SOI -20 250500 Athermal @ 1536 nm -25 PLOCAL =
Athermal @ 1576.8 nm [dB] Transmission 3.5 dBm 200400 -30
-35 150300 -40 1576.6 1576.7 1576.8 1576.9 1577 100200 Wavelength [nm]
10050 Resonance wavelength shift [pm] shift wavelength Resonance Thermal compensation of TPA 0 0 5 10 15 20 25 Local Power [dBm] ICTP Winter School, Trieste, 2014 A. Melloni