Marching towards a fully-integrated DWDM link for HPCs through ULTRALIT program

Di Liang Sr. Research Scientist, PI Large-Scale Integration Photonics (LSIP) Lab Hewlett Packard Labs

ARPA-E ENLITENED Phase 2 Kickoff Jan. 13 & 15, 2021

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Photonic Interconnected Exascale

2

racks can behave as a single server

100’s

Reduces energy

to move data

Reduces cost to move data

High-radix topologies

become possible

Optimizes bandwidth per

pin

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 HPE DWDM Photonics 2.0 - ULTRALIT (kickoff on 04/14/20)

ULTRA-ENERGY-EFFICIENT INTEGRATED DWDM OPTICAL INTERCONNECT (ULTRALIT)

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– Goal: A fully-integrated DWDM optical transceiver solution on silicon with over 1 Tb/s data rate and <1.5 pJ/bit energy efficiency at 50 oC (proposal goal)

Differential technical concepts: – DWDM+SDM with single QD source

– NRZ medium-BW modulation/λ

– Integrated III-V/oxide/Si MOS capacitor – Athermal & efficient channel control

(laser, modulator, deinterleaver, DEMUX) – Efficient NRZ modulation

– Ge and III-V co-integration on Si

– Multiple source and detector flavors – Monolithic, heterogeneous and a combined version – SiGe and QD avalanche photodetectors

Or wavelength deinterleaver [UCSB]

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 DWDM TRx system energy efficiency evaluation

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– 10/20λ-source with 60/30 GHz ch. spacing – 10 modulator/bank with 60 GHz ch. spacing – 40 ch. x 25 Gb/s (NRZ) = 1 Tb/s/chip – Goal: on(off)-chip comb laser WPE: >5%(10%)

SOA WPE: >10%(20%) <1 pJ/bit energy efficiency for both on- and off-chip

comb source configurations

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Multi-wavelength source development

Heterogeneous QD comb lasers on silicon (HPE)

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– Low-threshold operation （min Jth=163 mA/cm2)

– Flexible 15-100 GHz channel spacing design

– Record-large comb width: 3 dB: 12 nm; 6 dB: 18 nm; 10 dB: 25 nm

25 nm

>220λ, ∆λ=15.5 GHz

Kurczveil, FiO+LS FTu6E.6 (2020)

1x2 MMI 2x2

MMI Grating Coupler

Lcavity = 2.6 mm (FSR: 15.5 GHz)

SOA SOA SA

Lext = 780 µm

R=50%

R=100% LSOA = 1200 µm LSA = 176 µm

10 dB

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Multi-wavelength source development

Monolithic QD modelocked lasers and amplifiers on silicon (UCSB)

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SOA

MLL

0 100 200 300 400 5000

5

10

15

20

Pow

er (m

W)

Current (mA)

SA section floatingRoom temperature

Wavelength (nm)

Pow

er (d

Bm)

18λ, 60 GHz, Max. WPE: 10%

MLL

SOA

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 High-speed modulator development

Heterogeneous MOS capacitor microring modulators (built on the same chip with lasers)

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R=10 µm R=20 µm

R=10 µm, ER=5.6 dB

R=20 µm, ER=7.9 dB

28 Gb/s

RC-limited BW

Reference Type Mod. Rate (Gb/s) ER (dB) VπL

(V-cm) IL (dB)

Webster, OFC (2015) S-MZI 40 8 NA NA

Hiraki, Nat. Photon. 11, 482 (2017) H-MZI 32* 3.1 0.09 1

Thiessen, Opt. Expr. 27, 102 (2019) H-MZI 25 2.3 1 0.5

This work H-Ring 28 5.6 1 0.5

Sirinivasan, ECOC (2020)

S: silicon, H: heterogeneous * pre-emphasis drive signal

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Highly sensitive APD development

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SiGe APD Heterogeneous QD APD (laser epi)

20 Gb/s, 17.1 V

20 oC, 15 Gb/s (17 V)

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Preliminary link testing I (confidential)

Heterogeneous comb laser LiNbO3 modulator commercial InGaAs Rx

– 28-ch., 60-GHz comb laser

– External modulation up to 32 Gb/s limited by the pattern generator

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D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Preliminary link testing II (confidential)

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– All discrete lasers, modulators and detectors are fabricated in the same process

– 11-ch. comb laser MOSCAP modulator

– MOSCAP modulator heterogeneous QD APD

– I/O loss (6.5-10 dB/GC) and insertion loss from tunable filter (5 dB) huge link budget (≥ 28 dB for Tx, ≥38 dB for TRx)

– 2 optical amplifiers contribute too much noise

– Full TRx link test is on-going with SiGe APD

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Advanced integration platform development (confidential)

Direct epitaxy on a bonded III-V-on-silicon template

– Decouple intertwined mismatches in lattice, polarity and thermal expansion in heteroepitaxy.

– Enable seamless integration with SiPh PIC

– Potential appreciable cost saving by 300 mm-scale epitaxy and multiple regrowths

– Promising experimental results: – Record-low threading dislocation density of III-V epitaxy

on Si – Record-narrow PL FWHM on both III-V and Si substrate

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D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Bonus outcome, I

Widely tunable, narrow-Dl heterogeneous QD lasers

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Tran, APL Photonics (2020) Heterogeneous QD

Guo, CLEO PDP (2020) Malik, Photon. Research 8, 1551-1557 (2020) [Editor Pick]

52 nm (48-58 dB) ∆λ=5.3 kHz (10X improvement)

( )3

21spH

E

h nPQ Q

π νν α∆ = +

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Bonus outcome, II

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High-performance monolithic and heterogeneous DFB lasers

M: monolithic, H: heterogeneous

P1

N

P2

Vmos:-6:1:6 V

Wan, LPR 14, 2000037 (2020) Liang, IPC (postdeadline) (2020)

D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Program execution status

– Covid-19 impact: – Hiring freeze (postdoc, intern) – Comb laser and SiGe APD fab – Laser and SOA testing

– Risk mitigation: – Combined designs to minimize

fab runs – Relocated testing facility

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D. Liang @ ARPA-E ENLITENED Phase 2 Kickoff, 2020 Publication list

– Journal: 1. D. Liang, A. Descos, S. Srinivasan, C. Zhang, G. Kurczveil, Z. Huang, and R. Beausoleil, "High-Performance 1310 nm Quantum-Dot Distributed Feedback Laser with

Integrated Capacitive Control," Optica, 2021 (submitted). 2. Y. Wan, C. Xiang, J. Guo, R. Koscica, M. Kennedy, J. Selvidge, Z. Zhang, L. Chang, W. Xie, D. Huang, A. C. Gossard, and J. E. Bowers, "High speed evanescent quantum-dot

lasers on Si," Light: Science and Applications, 2021 (submitted). 3. A. Malik, J. Guo, M. A. Tran, G. Kurczveil, D. Liang, and J. E. Bowers, "Widely tunable, heterogeneously integrated quantum dot O-band lasers on silicon," Photonics Research

(Editor Pick), vol. 8, pp. 1551-1557, 2020. 4. Y. Wan, J. C. Norman, Y. Tong, M. J. Kennedy, W. He, J. Selvidge, C. Shang, M. Dumont, A. Malik, H. K. Tsang, A. C. Gossard, and J. E. Bowers, "1.3 µm Quantum Dot-

Distributed Feedback Lasers Directly Grown on (001) Si," Laser & Photonics Reviews, vol. 14, p. 2000037, 2020. 5. B. Tossoun, G. Kurczveil, Y. Yuan, A. Jones, C. Zhang, A. Descos, Z. Huang, A. Beling, J. C. Campbell, D. Liang, and R. G. Beausoleil, "InAs quantum dot waveguide

photodiodes heterogeneously integrated on silicon," Optica, vol. 6, pp. 1277-1281, 2019 – Conference: 1. Y. Wan, C. Xiang, R. Koscica, M. Kennedy, J. Guo, Z. Zhang, L. Chang, W. Xie, D. Huang, A. C. Gossard, and J. E. Bowers, "High speed evanescent quantum-dot lasers on

Si," in OFC, 2021 (submitted). 2. Y. Wan, J. Norman, Y. Tong, M. Kennedy, C. Shang, J. Selvidge, H. K. Tsang, A. C. Gossard, and J. E. Bowers, "1.3 µm regrown quantum-dot distributed feedback lasers on

(001) Si: a pathway to scale towards 1 Tbit/s " in CLEO, 2021 (submitted). 3. S. Srinivasan, D. Liang, and R. G. Beausoleil, "Heterogeneous SISCAP Microring Modulator for High-Speed Optical Communication," in ECOC Virtual, 2020, pp. paper Tu1B-7. 4. D. Liang, A. Descos, C. Zhang, G. Kurczveil, Z. Huang, and R. Beausoleil, "A Heterogeneous O-Band Quantum-Dot DFB Laser with Integrated MOS Capacitive Control " in

IEEE Photonics Conference (postdeadline) Virtual Conference, 2020. 5. B. Tossoun, S. Srinivasan, A. Descos, G. Kurczveil, D. Liang, and R. Beausoleil, "High-Speed III-V on Si Quantum Dot Avalanche Photodiodes with Polarization Dependent

Gain " in IEEE Photonics Conference Virtual Conference, 2020, p. ThE1.2. 6. S. Srinivasan, B. Tossoun, G. Kurczveil, Z. Huang, D. Liang, and R. Beausoleil, "160Gb/s optical link using Quantum-Dot comb laser source and SiGe APD," in IEEE

Photonics Conference Virtual Conference, 2020, p. MH1.2 7. J. Guo, A. Malik, M. A. Tran, G. Kurczveil, D. Liang, and J. E. Bowers, "Widely Tunable, Narrow Linewidth Quantum Dot Lasers heterogeneously Integrated on Silicon," in

CLEO (postdeadline) San Jose, CA, USA, 2020. 8. D. Liang, G. Kurczveil, Z. Huang, B. Wang, A. Descos, S. Srinivasan, Y. Hu, W. V. Sorin, S. Cheung, S. Liu, P. Sun, T. V. Vaerenbergh, M. Fiorentino, J. E. Bowers, and R. G.

Beausoleil, “Green Integrated DWDM Photonics for Next-gen High-performance Computing,” in OFC San Diego, CA, USA, 2020. – 3 patents 15