Microphotonics Readiness for Commercial CMOS Manufacturing Marco Romagnoli MicroPhotonics Consortium meeting MIT, Cambridge October 15 th, 2012
Passive optical structures based on SOI technology Building blocks Waveguide Directional coupler Microring Polarization splitter and rotator Fiber coupling Laser butt coupling Component AWG Echelle grating Lattice filter 2
Waveguide SiO2 Si Si (substrate) Single mode waveguide (TE mode) Buried (Si core SiO 2 cladding) Core Size ~ 200 x 500 nm Lower Cladding (BOX) Height 3 mm 3
Waveguide Loss Substrate leakage 25,00 20,00 25,0 TE Pol TM Pol α prop [db/cm] 15,00 10,00 5,00 0,00 12,3 8,0 9,2 6,7 13,1 2,7 8,2 2,3 4,5 2,5 3,7 2,5 2,3 2,5 150 200 250 300 350 400 450 500 550 600 650 700 750 Waveguide Width [nm] Weak guidance Scattering loss 2,0 1,8 3,4 2,4 3,5 1,2 Waveguide thickness = 220 nm 4
Waveguide Loss Line edge roughness (LER) Method monitoring s and L c based on SEM image analysis. Demonstrated a correlation between roughness, statistical parameters and propagation losses in a straight waveguide Lot # s (nm) L c (nm) 358 2.2 20 427 1.67 18 432 1.34 15 489 1.22 12 5
Waveguide Loss coherence length L c (nm) 160 140 120 100 80 60 40 20 α scattering [db/cm] 2.22789 4.45578 WG height = 220nm WG width = 450nm 2.22789 6.68368 8.91157 11.1395 13.3674 15.5952 4.45578 (λ = 1.55 µm, Pol = TE) 17.8231 20.051 22.2789 24.5068 6.68368 26.7347 15.5952 11.1395 31.1905 33.4184 35.6463 37.8742 40.1021 28.9626 24.5068 22.2789 20.051 17.8231 13.3674 8.91157 42.3299 44.5578 α [ db/cm ] 8 6 4 2 W = 400nm W = 450nm W = 500nm L C = 40nm 0 2.22789 1 2 3 4 5 6 standard deviation σ (nm) 0 0.5 1 1.5 2 2.5 σ [ nm ] Scattering losses increase with coherence length. Scattering losses decrease with waveguide width. 6
Waveguide Loss 1.7 ± 0.25 db/cm 12 SOI (2mm BOX), 65nm node at CNSE (University of Albany)
Waveguide Polarization Evolution STRAIGHT WAVEGUIDE TAPERED FIBER L = 6 mm TAPERED FIBER POLARIMETER W= 250nm 300nm 350nm 400nm 488nm TE TM 50 nm SCAN (1520-1570nm) waveguide thickness 220 nm 8
Directional Coupler For instance 2% error in coupling coefficient corresponds 2.6% in power splitting ratio. This error is mostly due to optical proximity effect. The error in gap-width is usually negligible. Proximity error 9
Microring Tolerances Parameter Effective index sensitivity 0.0017 /nm - 130 GHz/nm 0.0037 /nm - 270 GHz/nm Tunability c - 70 GHz/nm 10 GHz/ C W thickness W width Intrachip statistics on resonance fluctuation: = 27 GHz (0.22 nm) R Gap 12 SOI (2mm BOX), 65nm node at CNSE (University of Albany) W ring 10
Microring thermal tuning, trimming and power consumption M. R. Watts et al, CLEO/QELS 2009 2009 11
Microring athermal coupler 0.1 0.095 0.09 T = 25 C T = 125 C T = 225 C K Cross [normalized] 0.085 0.08 0.075 0.07 7.9%±0.4% 8.3% 7.9% 7.5% 0.065 0.06 0.055 1525 1530 1535 1540 1545 1550 1555 1560 1565 λ (nm) Athermal directional coupler Decrease of coupling coefficient with temperature is compensated for by increase of mode size at the new resonant wavelength. This feature implies that changes of filter shape are negligible in the 4 THz tuning range. 1542.3 nm 1550.0 nm 1557.7 nm Tx [db] -5-10 -15-20 -25-30 -35-40 -45-50 Thru T0 Drop T0 Thru Tmax Drop Tmax -55 193,750 193,850 193,950 194,050 194,150 194,250 Freq [THz] 12
Microring Tuning & Trimming 4 THz filter thermal tuning b) contact contact microheaters microheaters r ing First channel Last channel 13
Polarization Handling Polarization splitter & rotator 0-5 TM TE -10 Power (db) -15-20 -25-30 Residual TM Residual TM -35-40 1.5 1.52 1.54 1.56 1.58 1.6 Wavelength (mm) Spurious TE 14
Polarization Handling Polarization splitter & rotator performance Straight Si waveguide Polarization diversity scheme 0 SWG 0 PsP_T - 12 ASE_TE1nm -5-10 TM -5-10 ASE_TM1nm OVA_TE OVA_TM ASE_TE0,01nm Tx [db] -15-20 TE ASE_TE1nm ASE_TM1nm OVA_TE OVA_TM ASE_TE0,01nm ASE_TM0,01nm Tx [db] -15-20 ASE_TM0,01nm -25-25 -30 1520 1525 1530 1535 1540 1545 1550 1555 1560 1565 1570 Wavelength[nm] -30 1520 1525 1530 1535 1540 1545 1550 1555 1560 1565 1570 Wavelength [nm] 15
Fiber coupling Side view SM fiber 80 mm 2 modal area SiO 2 SMF SiO 2 :(Ge) 1 µm 220 nm Si waveguide Buried Oxide Si substrate Top view Input Taper Si Wg 0.1 mm 2 modal area (500 X 220 nm) Vertical Coupling SMF SiO 2 :(Ge) Tip 110 nm Silicon waveguide 500 nm 16
Fiber coupling Tolerances to mask misalignements and sensitivity to Si tip loss 2 25,00 Vertical coupling loss (db) 1.8 1.6 1.4 1.2 1 0.8 0.6 α prop [db/cm] 20,00 15,00 10,00 5,00 0,00 25,0 12,3 8,0 9,2 6,7 13,1 2,7 8,2 2,3 4,5 2,5 3,7 2,5 2,0 2,3 2,5 1,8 TE Pol TM Pol 150 200 250 300 350 400 450 500 550 600 650 700 750 Waveguide Width [nm] 3,4 2,4 3,5 1,2 10 db/cm Si tip loss 5 db/cm Si tip loss 0.4 0.2 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Mask misalignement (mm) TE/TM average loss 17
Grating coupler Fiber coupling Single polarization Dual polarization IEEE J. of Sel. Top. in Quant. El., 17, p. 597 (2011) 18
III-V DFB Laser Butt Coupling Air gap Gain Chip On submount Straight SOI waveguide w=1.4um Tapered Lensed fiber Spot size 1.7 um Working distance 4 um Butt-coupling alignment and no taper: InP/SOI best coupling loss = -4.2 db (experimental) (theoretical best case = -3.5 db) Extra 3 db loss with less than 1µm lateral offset and/or 3µm air gap Butt-coupling alignment with InP spot size converter (SSC) and taper on SOI: InP/SOI best coupling loss = -0.5 db (theoretical) Extra 1 db loss including less than 1um offset and/or 4µm air gap 19
AWG Laser Photonics Rev. 6, No. 1, 14 23 (2012) 20
Echelle Grating Laser Photonics Rev. 6, No. 1, 14 23 (2012) 21
Lattice Filters 22
thank you! email: marco.romagnoli@cnit.it