Integrated photonics for 2020 and beyond

Ray T. Chen

Microelectronics research Center

The University of Texas, Austin

Austin, TX 78758

&

Omega Optics Inc.

http://muri2.engr.utexas.edu/http://muri.engr.utexas.edu/

http://www.mrc.utexas.edu/people/faculty/ray-chenwww.omegaoptics.com

This Research is supported byNSF

AFOSRONR

US ArmyDARPANASANISTDOEEPANIH

Omega OpticsState of Texas2

12/17/2019 Page 3

Integrated Photonics application range 2020 and

Beyond

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1. Integrated Photonics for Optical

Computing

2. Integrated Photonics for Modulators

and Low loss Optical interconnects

3. Integrated Photonics for Lidar

Applications

4. Integrated Photonics for Biosensing

5. Integrated Photonics for Spectroscopy

6. Integrated Photonics for Broadband

EM- wave Sensors

12/17/2019 Page 5

Device

Modulator

comparison

[APL]

Multi-operand

logic gate

[in preparation]

AIG

[OE]

Full adder,

[OL/JSTQE]

Comparator

Shifter

Encoder/

decoderPlacement and

routing

[DAC]

WDM

[ASPDAC]

Cascading

problem

[in preparation]

Gate Circuit EPDA

Directed logic/EO logic

Disk/ring

Back

propagation

Feedforward

Neural Network

[ASPDAC]

Recurrent

Neural Network

[DAC,CLEO]

Devices Architecture Training

Neural network

Digital computing Analog computing

Optical computing

Convolutional

Neural Network

MZI

[DAC,ASPDAC]

On chip training

Tape outInternal fabrication/simulation Algorithm

Ising Model

Activation

function

Internal fabrication/simulation

Summary

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Schematic of the proposed AJ/B optical computing & interconnects on silicon

platform proposed by Texas MURI Center funded by AFOSR

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Instruction Fetch

Instruction Sequencing

Load Store

Fixed Point (add, shift, multiply)

Vector and Scalar

Decimal Floating point (add/multiply)

IBM Power-8 microprocessor floorplan

Replacing electronics with photonics in computing units

Optical computing and interconnect

12/17/2019 Page 9

Electrical full adder

Opticalfull adder

Latency of optical full adder

Latency of electrical full adder

,p g epbT nT T+ = ,p g sw opbT T T T n= + +

Reduced to

opb epbT T

Delay for generating P and G Switch time of modulators Optical propagation delay per bit Electrical delay per bit

𝑇𝑝,𝑔 𝑇𝑠𝑤 𝑇𝑜𝑝𝑏 𝑇𝑒𝑝𝑏

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Functional/Logic

Design

Circuit Design

Specification

Physical Verification

and Signoff

Physical Design

Proposed a new logic synthesis framework for PIC [ASPDAC’18]

Very limited tools. We developed a new CAD algorithm/tool for optical interconnect synthesis (DAC’18)

Design flow

12/17/2019 Page 11

Examples

𝑜𝑢𝑡 = (𝑎 + 𝑏)(𝑐 ⊕ 𝑑 + 𝑒)𝑓

Elements in library Circuit size Redundancy Generality

BDD Only one Large Large Yes

AIG Many, scalable Small Small No*

*with more and more new elements in library, it could apply to most of the cases with less circuit size and less redundancy.

12/17/2019 Page 12

Schematic of electrical and optical full adders

Reference:

Zhoufeng Ying, Zheng Wang, Zheng Zhao, Shounak Dhar, David Z. Pan, Richard Soref, Ray T. Chen, “Silicon microdisk-based full adders for optical

computing, " Optics Letters, 2018 (accepted).

Wang, Zheng, et al "Optical switches based carry-ripple adder for future high-speed and low-power consumption optical computing." In CLEO: Science

and Innovations, pp. STh1N-2. Optical Society of America, 2017.

Signal Symbol Transitional signals Expression Transfer function

Addends 𝐴𝑛, 𝐵𝑛 ‘Propagate’ 𝑃𝑛 𝑃𝑛 = 𝐴𝑛 ⊕𝐵𝑛 𝐶𝑛 = 𝑃𝑛 ∙ 𝐶𝑛−1 + 𝐺𝑛

Carry, Sum 𝐶𝑛, 𝑆𝑛 ‘Generate’ 𝐺𝑛 𝐺𝑛 = 𝐴𝑛 ∙ 𝐵𝑛 𝑆𝑛 = 𝐶𝑛−1⊕𝑃𝑛

12/17/2019 Page 13

MZIAbsorption

waveguideMicro-ring Micro-disk

Footprint ~2,000×500 μm2 ~40×10 μm2 ~10×10 μm2 ~5×5 μm2

Wavelength-

division

multiplexing

Multiple devices

with extra

MUX/DEMUX

Multiple devices

with extra

MUX/DEMUX

Multiple devices

only

Multiple devices

only

Industry maturityAvailable in PDKs

offered by foundries

Available in PDKs

offered by foundries

Available in PDKs

offered by foundries

Available in PDKs

offered by foundries

Insertion loss ~2.2 dB ~4.4 dB ~2.8 dB ~0.9 dB

Extinction ratio ~4.1 dB ~4.2 dB ~6.6 dB ~ 7.8 dB

Expected energy

consumption~750 fJ/bit ~20 fJ/bit ~50 fJ/bit ~1 fJ/bit

References:

1. E. Timurdogan, C. M. Sorace-Agaskar, J. Sun, E. Shah Hosseini, A. Biberman, and M. R. Watts, “An ultralow power athermal silicon

modulator,” Nat. Commun., vol. 5, p. 4008, Jun. 2014.

2. M. Pantouvaki, S. A. Srinivasan, Y. Ban, P. De Heyn, P. Verheyen, G. Lepage, H. Chen, J. De Coster, N. Golshani, S. Balakrishnan, P. Absil,

and J. Van Campenhout, “Active Components for 50 Gb/s NRZ-OOK Optical Interconnects in a Silicon Photonics Platform,” J. Light.

Technol., vol. 35, no. 4, pp. 631–638, Feb. 2017.

Candidates for EO modulators

12/17/2019 Page 14

2 213 13

4 8p pE CV CV= =

2 213 39

4 32G GE CV CV= =

21

4ME CV=

23Total P G ME E E E CV= + + =

23Total TotalP E f CV f= =

• Timurdogan, E., et al. Nature communications, 5(2014).

• http://userweb.eng.gla.ac.uk/fikru.adamu-lema/Chapter_02.pdfBased on 32 nm node library

Power consumption and latency for electrical and optical full adders

17C fF= 0.5V V=

𝐸𝑃 Energy for generating P

𝛼𝑃 Activity coefficient for P

𝐸𝐺 Energy for generating G

𝛼𝐺 Activity coefficient for G

𝐸𝑀 Energy for modulators

𝐸𝑡𝑜𝑡𝑎𝑙 Total energy

𝑃𝑡𝑜𝑡𝑎𝑙 Total power

𝐶 Modulator capacitance

𝑉 Swing voltage

𝑓 Frequency

Tp,g Delay for generating P and G

𝑇𝑠𝑤 Switch time of modulators

𝑇𝑜𝑝𝑏 Optical propagation delay per bit

𝑇𝑡𝑜𝑡𝑎𝑙 Total latency

,total p g sw opbT T T T n= + +

, 12 ,p gT ps= 0.6opbT ps=50 ,swT ps=

12/17/2019 Page 15

The fabrication for the high-speed

full adder is very complicated, for

example, there are 24 masks in total

including six times P/N implant

steps.

Cross-section Fabrication complexity

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Quantity: 20 chips

Size: 2 mm*4 mm

AIM chips

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The top view of the whole chip

2-bit full adder

4-bit full adder

4 mm

2 m

m

Testing area

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Microdisk and MMI Crossing

Phase shifter Grating coupler

100um

100um

Photodetector

Waveguide and splitters

25

um

Microdisk

MMI

90:10 splitters

40um

20um

15um100um

12/17/2019 Page 19

Experimental results

10Gb/s 20Gb/s Truth table

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Multi-operand logic gate

MOLG-4

a b c d Y

0 0 0 0 0

0 0 0 1 1

...

1 1 1 1 1

a b c d Y

0 0 0 0 1

0 0 0 1 0

...

1 1 1 1 1

𝑦 = 𝑎 + 𝑏 + 𝑐 + 𝑑

𝑦 = 𝑎ത𝑏 ҧ𝑐 ҧ𝑑 + ത𝑎𝑏 ҧ𝑐 ҧ𝑑 …

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Total functions

22𝑛

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3.SOA; 6.Curve; 7.Crossing; 8.Splitter5. 1x2 Splitter1.Laser; 2. PD; 3. SOA 1. Laser; 4. EAM

InP chipInP platform: monolithically integrated system

with lasers, modulators, and photodetectors

300um300um

300um

1 2

3 2

4 13

56

78

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Encoder/decoder

Comparator

Shifter

Second run

4 mm

2 m

mSchematic of a typical ALU

12/17/2019 Page 25

MZI-based Optical Neural Networks

V*U Σin σ out

W

Input

layer

Hidden

layer

…

Output

layer

• Shen, Yichen, et al. "Deep learning with coherent nanophotonic circuits." Nature Photonics, 2017.

MZI for 2-dimensional unitary

Singular value decompositionW = U Σ V*

MZI array for unitary U and V*

…

…

…Ti,j

in out• Bigger matrices are more

sensitive to phase noise

• Black, blue, red boxes represent phase noise standard deviation of 0.05, 0.02, and 0.01

Improve Phase Robustness & Scalability

Classical architecture Slimmed architecture

• Architectural improvement

ΣT Uin σ outV*U Σin σ out

12/17/2019 Page 28

1. Integrated Photonics for Optical

Computing

2. Integrated Photonics for Modulators

and Low loss Optical interconnects

3. Integrated Photonics for Lidar

Applications

4. Integrated Photonics for Biosensing

5. Integrated Photonics for Spectroscopy

6. Integrated Photonics for Broadband

EM- wave Sensors

29

EO polymer modulator

30

Measurement setup

• The bandwidth is measured to be > 40GHz.

• The capacitance is ~0.4fF.

• The energy consumption per bit can achieve

CV2/4=2.5 fJ/bit for 6dB extinction ratio.

31

Sid

e-

lobes

RF

resp

onse

Modula

tion

index

SEO125AuSiO2Si

G S G

C C

Measurement Results

32

SWG Strip PC Slot Slot Plasmonic

Structure Ring Ring MZI MZI Ring MZI

Nonlinearity 𝐫𝟑𝟑 54.7 pm/V64 pm/V

[2]98 pm/V [3] 104 pm/V [4]

30 pm/V

[5]230 pm/V [6]

Mode overlap* 36.2% ~4% ~6.1% ~31.9% ~31.9% ~90%

Propagation loss∼3.0 dB/cm

[1]

0.2–2

dB/cm [2]N/A

~7.5 dB/mm

[4]

35 dB/cm

[5]200 dB/mm [6]

Bandwidth >40GHz 3 MHz [2] 15 GHz [3] 18 GHz [4] 1 GHz [5] >60 GHz [6]

Power

consumption2.5 fJ/bit N/A

94.4 fJ/bit

[3]19 fJ/bit [4] N/A ~18 fJ/bit [6]

Footprint 70um *29um40μm

(radius) [2]

300 um

(length) [3]

1.5 mm

(length) [4]

60 um

(radius) [5]

29 um (length)

[6]

*The mode overlap is calculated based on the structure in the reference.

Comparison between SOH

modulators

12/17/2019 Page 33

1. Integrated Photonics for Optical

Computing

2. Integrated Photonics for Modulators

and Low loss Optical interconnects

3. Integrated Photonics for Lidar

Applications

4. Integrated Photonics for Biosensing

5. Integrated Photonics for Spectroscopy

6. Integrated Photonics for Broadband

EM- wave Sensors

Motivation

34

Point-to-Point CommunicationSurveying and Mapping

Lightweight, compact, low power consumption,

and large angle agile beam steering

http://www.cablefreesolutions.com

http://ngom.usgs.gov/

Cr/Au

Silicon

Polysilicon

16 Independent

TO Phase shifters

Input

Grating

CouplerCascaded 1x2

MMIs

Wire

Bonding

Pads

Output gratings with

polysilicon overlay

Steering in XY plane-TO phase tuning.

Steering in XZ plane-wavelength tuning.

OPA with Poly Overlay

Completed Device

36

ψ

θ

2cm

http://www.mrc.utexas.edu/people/faculty/ray-chen

2D Beam Steering

37

38

MONOLITHIC OPTICAL PHASED ARRAY AT MID-IR FOR LIDAR APPLICATIONS

Taper Region

QCL

FABRICATED OPA

39

FABRICATED OPA

40

d = 13.73

m

w = 3.29 m

= 1.55 m

PHASE SHIFTER CHARACTERISTICS

41

𝑃𝜋225mW

To be reduced by optimization.

BEAM STEERING MEASUREMENT SETUP

42

QCLOPA

SCREEN

Phase Shifter

Controller

mai

n

lob

e

gratin

g lobe

MID-IR Camera

AZIMUTHAL ANGLE STEERING

43

Max Steering Angle=19.2 0

HPFW=0.5 0

Spot Resolution=19.2/0.5=38

=00

=180 0

=00

=-90 0

44

45

12/17/2019 Page 46

1. Integrated Photonics for Optical

Computing

2. Integrated Photonics for Modulators

and Low loss Optical interconnects

3. Integrated Photonics for Lidar

Applications

4. Integrated Photonics for Biosensing

5. Integrated Photonics for Spectroscopy

6. Integrated Photonics for Broadband

EM- wave Sensors

Opal, the best known periodical

structure in nature.

Photonic Crystal Structures in Nature

and in Nanofabrication

47

48

64 Highly Multiplexed Early Cancer

Detection Chip

Eigenvalue

Problem

Schrődinger EquationMaxwell’s Equations

Periodic atomic structure(Natural)

Electronic Bandgap

Semiconductors

Introduction of defects

Trapped Carriers

Periodic variation of

refractive index (Artificial)

Photonic Bandgap

Photonic Crystals

Introduction of defects

PC resonant cavities

and waveguides

ω

k k

1000

{ }

Photonic Bandgap Electronic

Bandgap

hν

Photonic Dispersion

Electronic Dispersion

Photonic Crystals and Defects

SINECAD Center Overview 50

Silicon Nanophotonic Biosensor Chip for Lung

Cancer Detection

Figure of merits of our cancer detection chip in reference to all existing results [1-12]

[1] J. Waswa, J. Irudayaraj, C. Deb Roy, “Direct detection of E-Coli O157: H7 in selected food systems by a surface plasmon resonance biosensor”, LWT-Food Science and

Technology 40 (2), 187 (2007).

[2] M.G. Scullion, et al., “Slotted photonic crystal cavities with integrated microfluidics for biosensing applications”, Biosens. Bioelectron. 27, 101-105 (2011).

[3] S. Mandal, D. Erickson, “Nanoscale optofluidic sensor arrays”, Opt. Exp.16(3), 1623 (2008).

[4] S. Pal, et al., “Silicon photonic crystal nanocavity-coupled waveguides for error-corrected optical biosensing”, Biosens. Bioelectron. 26, 4024 (2011).

[5] C.F. Carlborg, et. al, “A packaged optical slot-waveguide ring resonator sensor array for multiplex label-free assays in labs-on-chips”, Lab on a Chip 10, 281 (2010).

[6] K. De Vos, et al., “Silicon-on-insulator microring resonator for sensitive and label-free biosensing”, Opt. Exp. 15 (12), 7610 (2007).

[7] C.A. Barrios, “Optical slot-waveguide based biochemical sensors”, Sensors 9, 4751 (2009).

[8] S. Zlatanovic, et al., “Photonic crystal microcavity sensor for ultracompact monitoring of reaction kinetics and protein concentration”, Sens. and Actuators B 141, 13-19 (2009).

[9] H. Li, X. Fan, “Characterization of sensing capability of optofluidic ring resonator biosensors”, Appl. Phys. Lett. 97, 011105 (2010).

[10] B.T. Cunningham, et al, “Label-free assays on the BIND system”, J. Biomol. Screen. 9, 481 (2004).

[11] M. Iqbal, et al., “Label-Free Biosensor Arrays based on silicon ring resonators and high-speed optical scanning instrumentation”, IEEE J. Sel. Top. Quant. Electron. 16(3), 654 (2010).

[12] Y. Zou, S. Chakravarty, W-C. Lai, R.T. Chen, “High yield silicon photonic crystal microcavity biosensors with 100fM detection limit”, Proc. of the SPIE 8570, 857008 (2013) and S.

Chakravarty, Y. Zou, W-C. Lai, R.T. Chen, “Slow light engineering for high Q high sensitivity photonic crystal microcavity biosenors in silicon”, Biosensors and Bioelectronics 38(1), 170 (2012).

And blocking

with 1% BSA

APTES

Piranha acid sol,

At 60 ⁰C, 1 hour

I. sacrificial

oxidation

II. 48HF acid

for 5 min

Surface Functionalization

Probe Immobilization

Probe-Target Reaction

51

Biochip Preparation and Detection Procedure

12/17/2019 Page 52

Biomarkers so far has been detected

Breast cancer biomarkersLung Cancer BiomarkersPancreatic Cancer BiomarkersThree Antibiotic drugHeavy metal attached biomarkers

Selective CTC Capturing

Light In

Light Out

Silicon Nanophotonic Devices for Early

Cancer Detection

Integrated Sample Preparation and Sensors on a Chip

with User-Friendly Machine-Human Interface

Fast PlasmaSeparation

on Chip

Sample Preparation on ChipSensor Arrays on Chip

12/17/2019 Page 54

12/17/2019 Page 55

1. Integrated Photonics for Optical

Computing

2. Integrated Photonics for Modulators

and Low loss Optical interconnects

3. Integrated Photonics for Lidar

Applications

4. Integrated Photonics for Biosensing

5. Integrated Photonics for Spectroscopy

6. Integrated Photonics for Broadband

EM- wave Sensors

56

Atmospheric Absorbances

Atmospheric Transparency Windows and Absorbing Molecules of Interest

Courtesy: Daylight Solutions

57

Principle is based on Beer-Lambert absorption law:

]exp[0 LII −=

• L = Geometrical optical path length <1mm

• = Absorption factor from dispersion enhanced light-matter interaction

gv

ncf

/=

• vg = Group velocity of light

in PCW

• f = Electric field intensity

enhancement in the slot at

center of PCW

Others Parameters Omega Optics

Need multi-pass gas cells Gas Cells Optical Overlap with Analyte

on-chip, no gas cells needed

High

Finesse/Reflectivity

Mirrors to Enhance

Optical Path Length

Mirrors No mirrors, Slow Light

Enhanced Optical Path with

Slotted Photonic crystal

waveguide on Chip

Precise/Fragile Optical

Alignments needed

Optical

Alignments

All components aligned in

fabrication

Heavy Weight <2lbs (battery)

bench tops >$25,000 Cost <$5,000

Slow Light Enhanced Infrared Absorption

Spectroscopy

58

Silicon

QC

DQCL

Sapphire

Slotted PCWs

QCL successfully bonded to

silicon on sapphire, and

emission coupled to silicon;

Monolithic Integration for Absorption

Spectrometry l=3-5m

QCD ResponseQCL Response

THIS PAPER

NASA Phase 1 Final Report

Swapnajit Chakravarty, Misha Belkin and Ray Chen,

NASA Final Report Contract #: NNX17CA44P, 2018

Triethyl Phosphate (TEP) Gas Sensing

59

Slot

Waveguide

Slot

Waveguide

Ridge

Waveguide

60

12/17/2019 Page 61

1. Integrated Photonics for Optical

Computing

2. Integrated Photonics for Modulators

and Low loss Optical interconnects

3. Integrated Photonics for Lidar

Applications

4. Integrated Photonics for Biosensing

5. Integrated Photonics for Spectroscopy

6. Integrated Photonics for Broadband

EM-wave Sensors

We Deliver Innovation

20 µm 10 µm

Gold antenna

Silicon slot PCW

Antenna/silicon overlap

2 µm

• Tilted view • Tilted view (magnified)

• Top view of mode converter and slot photonic crystal waveguide

Broad band EM wave Sensor

12/17/2019 EM Wave Sensor 62

We Deliver Innovation

• Devices before and after polymer spincoating

EO polymer

Silicon

Box

Air

SlotPCs

PCs

• EO polymer infiltration

• Cross-sectional SEM image of EO polymer infiltration

• EO polymer poling

• Purpose: To activate electro-optic effect• Condition: (1) Glass transition temperature: e.g. 150oC.

(2) DC Electric field: e.g. 100V/um• Results: To assemble chromophores into a uniform order

(noncentrosymmetric order with EO effect)

• EO effect (Pockels effect)

r33: EO coefficient

Vp

150µm

• Maximum Leakage Current Density: 8.8 A/m2

• Small leakage current → high poling efficiency

3

33

1

2n n r E =

Electro-optical Polymer

12/17/2019 EM Wave Sensor 63

0 100 200 300 400 500 600 7000.0

0.2

0.4

0.6

0.8

1.0

Time (sec)

Le

ak

ag

e c

urr

en

t (n

A)

-30

0

30

60

90

120

150

Te

mp

era

ture

(oC

)

We Deliver Innovation

Driving RF signal

Modulated optical signal

Vπ =0.94V

50/50 combiner

Laser

90/10 splitter

Function generator

VOA

MSA

Detector

VOA: variable optical attenuator

• Testing system

• Measured modulation response • Measured transfer function

✓ Vπ × L = 0.0282 V×cm✓ Record-high effective in-

device EO coefficient :

33, 3

weffective

Sr

n V L

l

= = 1230 pm/V

• High EO modulation efficiency

Electro-optic Modulator

12/17/2019 EM Wave Sensor 64

f =100KHz

Combined enhancements: • Large r33 of EO polymer• High poling efficiency• Enhanced by slow-light effect

12/17/2019 Page 65

Thank you !