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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
12/17/2019 Page 4
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
12/17/2019 Page 7
Schematic of the proposed AJ/B optical computing & interconnects on silicon
platform proposed by Texas MURI Center funded by AFOSR
12/17/2019 Page 8
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
12/17/2019 Page 10
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
12/17/2019 Page 16
Quantity: 20 chips
Size: 2 mm*4 mm
AIM chips
12/17/2019 Page 17
The top view of the whole chip
2-bit full adder
4-bit full adder
4 mm
2 m
m
Testing area
12/17/2019 Page 18
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
12/17/2019 Page 20
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 …
12/17/2019 Page 21
12/17/2019 Page 22
Total functions
22𝑛
12/17/2019 Page 23
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
12/17/2019 Page 24
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 !