A 10 Gb/s Photonic Modulator and WDM MUX/DEMUX Integrated with Electronics in 0.13um SOI CMOS High Speed Circuits & Systems Laboratory Joungwook Moon

Contents Introduction 1. Implementation 2. Conclusion 3.

Introduction Author :Andrew Huang. Luxtera, Carlsbad, CA (ISSCC 2006) Manufacturable yield-frendly photonics components combined with electronics using a 0.13um SOI process for PowerPC processors A 10Gb/s optical modulator integrated with a driver and 4-channel WDM MUX/DEMUX w/ integrated tuning circuits – WDM MUX/DEMUX(Wavelength division multiplexing) : To increase capacity and speed of commucation, different kind of data put into a single fiber. An optical fiber can carry maximum 80 wavelength of data.

Implementation - Waveguide C-band (1.5um) optical waveguides are formed by a high reflective index core of transparent silicon & low reflective index index silicon dioxide C-band (conventional wavelength band) :1530nm ~ 1565nm Waveguide structure & Optical Ref.[2] Wavelength Band

Holographic Lens Holographic lens(HL) couples light normal to the surface of the die with < 1.5dB loss HL allows inexpensive wafer scale testability (Good replacement for the refract- -ing lens in maching application) 10um fiber core waveguides SEM photograph of a holographc lens Holographic lens

Modulator (1) Modulator uses a free-carrier-effect-based device in a Mach-Zender interferometer -Light is split evenly into two arms. -The light is phase-modulated. -Differential accumulation of phase (ΔΦ) causes the recombined light to interefer. P= cos(∏/2 + ΔΦ)/2 Schematic diagram of a phase modulator in one arm of the MZI A reverse-biased lateral PIN diode (contrast to conventional method based on diffusion/recombination) The speed of the resulting device is limited by RLC

Modulator (2) In a lumped configuration, junction length needed for sufficient phase shift would be parastic-limited to < 10Gb/s  To overcome this lumped-RC speed limit is to design a travelingwave electrode. (designed as a part of the microwave transmission line) On chip terminations are integrated at the end of the microwave transmission lines to supperss back- relfections The characteristic impedance of the transmission line + PN diode : Total system impedance = 25 Ω The modulator has a length of 2mm, microwave loss would be sufficiently small

Integrated Driver A cascoded thin-gate-oxide transister swich is used Pre-driver chain drives the switch transistor Cascode device is used to shield the high-performance switch from the relatively high voltages required by the modulator elements Integrated driver connected to one MZI arm The active area for the modulator driver is 0.08mm 2 Total area is 2.6mm 2 including 2mm modulator, termination network, and pads CMOS optical modulator with Differential Driver

Integrated Driver A cascoded thin-gate-oxide transister swich is used Pre-driver chain drivesthe switch transistor Cascode device is used to shield the high-performance switch from the relatively high voltages required by the modulator elements Optical eye of integrated modulator plus driver at 10Gb/s The integrated circuit yields a BER with a PRBS at 10Gb/s. Performance of the optical modulator is entirely limited by the driver

4-Channel DWDM AWG (1) A Key Advantage of integrated electronics and photonics on a single chip is to raise yield of an optical device by electronic control ciucuitry Optical 4-channel DWDM AWG with an 8b DAC array is integrated (< 0.6mm 2 ) DWDM: Dense Wavelength Division Multiplexing AWG: Arrayed waveguide grating  generate a desired spectral function Die shot of DAC array plus AWG element Electrically Tunable AWG

4-Channel DWDM AWG (2) Forward-biased PIN junction phase Modulators integrated into each arm of the AWG.  offer great phase efficiency (90 ° /mA for 100um arm) but lower speed & higher loss Each modulator is driven by an 8b 5/3 segmented DAC to restore phase relationship (inducing random delay) After tuning, the crosstalk suppression is improved by over 16db

Luxtera CMOS Photonic Tech. from Luxtera (

Conclusion Abstract – Motolithic integration of both photonic and electronic components operating at 10Gb/s in a 0.13um SOI CMOS process – A modulator uses free carrier plasma dispersion in a reverse-biased PIN optical phase shifer in a Mach-Zender interferometer. – An AWG demultiplexer uses a forward- biased PIN phase shifter to compensate the optical path length improving the channel separation