1 A 3.9 ns 8.9 mW 4×4 Silicon Photonic Switch Hybrid-Integrated with CMOS Driver A. Rylyakov, C. Schow, B. Lee, W. Green, J. Van Campenhout, M. Yang, F. Doany, S. Assefa, C. Jahnes, J. Kash, Y. Vlasov IBM T.J. Watson Research Center, Yorktown Heights, NY
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A 3.9 ns 8.9 mW 4×4 Silicon Photonic Switch Hybrid-Integrated
with CMOS Driver
A. Rylyakov, C. Schow, B. Lee, W. Green, J. Van Campenhout, M. Yang, F. Doany, S. Assefa, C. Jahnes, J. Kash, Y. Vlasov
IBM T.J. Watson Research Center, Yorktown Heights, NY
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Outline
• Motivation• Silicon photonics technology overview• Integration strategies: full monolithic and hybrid• 4×4 switch hybrid-integrated with CMOS driver• Conclusion
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Motivation• Goal: develop photonic device process compatible with CMOS
– enables high-speed, high-density interconnects forlower power, lower cost, long reach communication
– opens up a number of new applications (biomedical, sensor, etc)
• Hybrid integration (flip-chip or wirebond) of Si photonic devices and electrical circuits:– ideal for early prototyping– important step towards full integration– either hybrid or monolithically integrated could be commercialized
• A 4×4 switch requires the development of all key components, highlights the advantages of the silicon photonic technology:– data stays in the optical domain – multiple data streams routed in the same device (WDM)
Measured Optical Switching Times of a CMOS Driven 2×2 MZI switch
B. G. Lee, et al. (CLEO 2010)
19NIN
SIN
WIN
EIN
MZI 3
MZI 2
MZI 1
MZI 6
MZI 5
MZI 4
CM
OS
chi
pP
hoto
nic
chip
WOUT
NOUT
EOUT
SOUT
NIN
NO
UT
SO
UT
SIN
WIN
WOUT
EOUT
EIN
model
function
4×4 Switch and CMOS Driver Block DiagramSerial Interface
512 µm1330 µm
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4×4 Switch Configuration States
MZI3
MZI2
MZI1
MZI6
MZI5
MZI4
0
0
1
0
0
1
0
0
1
MZI4
0
0
1
0
0
0
1
0
1
MZI3
0
1
0
0
1
1
1
0
0
MZI2
20105
40114
41103
21012
41011
PowerMZI6MZI5MZI1State
00009
10008
20007
10106
EIN
SIN
WIN
NIN
WOUT
NOUT
EOUT
SOUT
Of the 26=64 possible states of the 2×2 switches, only 9 are unique. The equivalent states of the 4×4 switch differ by static power dissipation (number of 2×2 switches “ON”)
In all 9 configuration states, worst case crosstalk between channels is less than -10 dB,insertion loss ~6 dB, off chip coupling loss ~1 dB.
Area: 300 × 1600 µm2 (relaxed layout)
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Digital 90-nm CMOS DriverRCONTACT
I(τ)C(Q)
• Electrical model of the p-i-n diode includes contact resistance, non-linear charge-dependent capacitance and carrier lifetime-dependent current source
• Designed to drive a wide range of capacitive loads and steady state currents with ample speed for switch applications
VDD = 1.2 V
500 ps
×1 ×2 ×16
from serialinterface
512 µm1330 µm
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6
CMOS chip
p-i-n diode model
Photonic chip
ON/OFF
optical function
Electrical performance of the CMOS driver
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150 µm
North
SouthWest
East
South
North
East
West
Drivers with predrivers
Serial Interface
4×4 Switch and CMOS Driver Die Photos
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CMOS IC
Photonic chip
IC probe pads on bottom
(not visible)
optical coupling
Hybrid Packaging of CMOS and Photonics
~50 µm tall
75 µm pads, 150 µm pitch
~30 µm tall
solder reflowed again to collapse columns into balls
Photonic chip pads
Ni-Au Pad Metallization:
Solder Transfer
• eutectic SnPb solder (260-300°C) plus forming gas
• ~25-30 g/bond obtained
Flux-Free Solder Process:
CMOS chip pads
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North Output
South Output
EastInput
West OutputNorth OutputEast OutputSouth Output
West Output
East OutputSouth Output
North OutputWest Output
East Output
All 6 MZI’s OFF —West Output
MZI 6 ON (1.02V)—North Output
MZI 2 ON (1.05V)—South Output
EastInput
EastInput
Infrared Images of Static Optical Switching
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North Output
East Input
South Output
East Output
West Output
South InputNorth Input West Input
NoU-Turn
NoU-Turn
NoU-Turn
NoU-Turn
NoU-Turn
NoU-Turn
NoU-Turn
NoU-Turn
λ att1531 nm
40 Gb/smodulator RX
4×4 Photonic SwitchEDFA
Measured routing of 40 Gb/s data
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East Input
1543 nm
North Output
South Output
West Output
1537 nm1531 nm
40 Gb/smodulator
4×4 Photonic Switch
RX
1531 nm
1537 nm
1543 nm
EDFA EDFA
λ att
Measured routing of 3 × 40 Gb/s WDM data
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Measured Power Sensitivity Curves
All wavelength channels, all output configurations of the 3 × 40 Gb/s signal tested, showing ~0.5 dB spread at 10-12 BER
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Conclusion• Full set of CMOS compatible photonic devices:
– waveguides, splitters, couplers, crossings, WDM structures, etc.– waveguide coupled integrated Ge photodetectors– MZI and ring based switches, modulators
• High-density, low-loss edge fiber coupling demonstrated– 8 parallel fibers coupled to on-chip waveguides on 20 µm pitch
• Monolithically integrated technology announced in December 2010
• Recent CMOS driven hybrid-integrated results include a 15 Gb/sreceiver and a ring modulator based 8 Gb/s transmitter