solid state lidar using the leti silicon ......solid state lidar using the leti silicon photonics...
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SOLID STATE LIDAR USING
THE LETI SILICON
PHOTONICS PLATFORM:
PROGRESS AND PERSPECTIVES
Daivid FowlerDepartment of Optics and Photonics, LETI
25/06/2019
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OVERVIEW
• LIDAR and Optical Phased Arrays
• Ongoing and future development
• Initial 2D beam-scanning demonstration using an
OPA based on LETI silicon photonics
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• RADAR λ = 10-2 to 102m
• LIDAR λ ~ 10-6m
• smaller wavelength leads to improved spatial resolution
• Applications: Automotive, aviation, archeology, etc.
INTEGRATED LIDAR
LiDAR = Light Detection And Ranging
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INTEGRATED LIDAR SYSTEM
scene
• Emitter
• Free space optics
• Photodetection
• Image processing
• Drive electronics
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INTEGRATED LIDAR EMITTER
• Mobile source RADAR • Phased array RADAR
Optical
Phased
Array
• Solid state LIDAR• Mobile source LIDAR
• Silicon photonics
• Lens free
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Near-field
Quasi-uniformillumination
𝐼(𝜃) = 𝐹𝑇 𝐴 𝑥
OPTICAL PHASED ARRAY BASIC PRINCIPLE
Far-field
I(θ)
θ
x
Point source
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ampl
phase
Near-field
Cosinusoidalillumination
𝐼(𝜃) = 𝐹𝑇 𝐴 𝑥
Two CoherentPoint sources
I(θ)
θ
x
Far-field
OPTICAL PHASED ARRAY BASIC PRINCIPLE
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Near-field
ShiftedCosinusoidalillumination
𝐼(𝜃) = 𝐹𝑇 𝐴 𝑥
OPTICAL PHASED ARRAY BASIC PRINCIPLE
Far-field
ampl
phase
I(θ)
θ
x
Two out-of-phase coherentPoint sources
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ampl
phase
Near-field 𝐼(𝜃) = 𝐹𝑇 𝐴 𝑥Far-field
Many coherentPoint sources (d>>λ)
I(θ)
θ
x
OPTICAL PHASED ARRAY BASIC PRINCIPLE
Multiple narrow peaks
d>>λ
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Near-field 𝐼(𝜃) = 𝐹𝑇 𝐴 𝑥Far-field
single narrowpeak
Many coherentPoint sources (d ~ λ)
I(θ)
θ
x
ampl
phase
d ~ λ
OPTICAL PHASED ARRAY BASIC PRINCIPLE
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Near-field 𝐼(𝜃) = 𝐹𝑇 𝐴 𝑥Far-field
single narrowpeak
Many coherentPoint sources (d ~ λ)
I(θ)
θ
x
ampl
phase
d ~ λ
OPTICAL PHASED ARRAY BASIC PRINCIPLE
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EXAMPLE OF OPTICAL PHASED ARRAY DIMENSIONS
• Operating wavelength, λ = 1µm
• 10cm object at 100m
• Unambiguous sweeping range +/-45°
, Φ (deg)
~1000 sources, each
separated by 1µm
d
n = 1 2 3 N
w
>90° between diffraction orders
ΔΦ ΔΦ = 90°
d = λ/sin(ΔΦ) = λ
Beam divergence ~ 1mRad ~ 0,05°
Φ3dB
Φ3dB = 1mRad,
N.d = 1,22λ/ Φ3dB = 1220 x λ
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INTEGRATED OPA USING SILICON PHOTONICS
phase
tuningPower splitter
Laser inputEmitter array
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INTEGRATED OPA USING SILICON PHOTONICS
Silicon photonics:
• Operating wavelength 0,5-
4µm
• Suited to high component
density
• CMOS compatible for high-
volume/low cost production
phase
tuningPower splitter
Laser inputEmitter array
Solid state beam scanning (in Ф)
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INTEGRATED OPA USING SILICON PHOTONICS
phase
tuningPower splitter
Laser inputEmitter array
What about the second dimension (θ)?
Silicon photonics:
• Operating wavelength 0,5-
4µm
• Suited to high component
density
• CMOS compatible for high-
volume/low cost production
Solid state beam scanning (in Ф)!
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OPA FOR TWO DIMENSIONAL BEAM STEERING
2D antenna array
• Need a point source
with an area < λ2
• NxN phase controls
Other solutions
• OPA + Ph crystals
• OPA + liquid crystals
• VCSEL arrays
• etc
Watts, MIT
Abiri, CIT
Yoo, Berkeley
Tuneable laser
• ~10nm per degree in θ
• need laser with a λ
range >100nm
Van Acoleyen, IMEC
Bowers, UCSB
Kwong, Uni of Texasθ
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• Multi-1D OPA
• One OPA per θ value
• Single source plus switch
• 2D beam steering at a
single wavelength with
a single laser
• Discrete sweeping in θ
• θ range/resolution limited
by OPA footprint
OPA FOR TWO DIMENSIONAL BEAM STEERING
θ =+15°
θ =+13°
θ =-15°
…
Velodyne VLP-16
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OPA FOR TWO DIMENSIONAL BEAM STEERING
• 905nm OPA based on SiN
waveguides/devices
N. A. Tyler et al. Optics Express, Feb. 2019.
Tyler, N. A., et al. CPMT Symposium BEST PAPER AWARD
• ‘2D’ beam steering at 905nm
demonstrated
• Wafer-scale automatic test facilities
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Sweeping range Φ/θ
resolution Φ/θ
1st LETI demo
(2018)
±17°/3°
4°/1°
2019 target
(In fabrication)
202? Target
± 30/8°
0,3°/1°
± 60/20°
0,1°/0,1°
• Change to ‘cooler’ phase modulator mechanism
• Reduce antenna pitch, increase channel number
• Reduce optical path length and/or Reduce WG phase errors
Circuit loss
Sweep frequency
Voltage per channel
-15dB
10KHz
1
mW per channel 80
-3dB
10KHz
<1
<-1dB
10MHz
<<1
20 <1
LETI OPA DEVELOPMENT AND PERSPECTIVES
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1550nm Si 900nm SiN 900nm SiN 900nm SiN
900nm
SiN
1550nm
Si
2016 2017 2018 2019
2019 onwards• IRT (National French funding)
• ECSEL VIZTA (European funding)
• Industrial clients
LETI OPA DEVELOPMENT AND PERSPECTIVES
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LETI LIDAR SYSTEM DEVELOPMENT
• CEA-LETI HAS THE CAPABILITY TO MAP THE LIDAR INTEGRATION STRATEGY
• THE OPA IS ONE OF THE (MANY) KEY TECHNOLOGIES
TECHNOLOGIES SYSTEM
VCSEL EEL
MEMs
mirrorOPA
APDs SiPM
Fiber
laser
Pulse
AVGAnalog
IC
Hetero-
dyne
Time to
Digital C
LensMEMs
mirror
Sigma
fusion
Sensor
fusion
Embedd
ed AI
Rotating
mirror
Feedbac
k loops
Optical source
Beam steering
Photodetection
System integration
Optics (Tx, Rx)
Data processing
PiNSPADs -
Gm
System driven device development
CO-DESIGN SOFTWARE-HARDWARE
WITH TEST BENCHES
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SUMMARY
• LIDAR systems for high resolution 3D imaging
• Demonstration of 2D beam-steering at 905nm using
a CMOS compatible Optical Phased Array circuit
• Significant future development to achieve target
system specifications
• Ongoing LETI development now guided by a system
based approach
• Optical Phased Arrays for solid-state beam scanning
Leti, technology research institute
Commissariat à l’énergie atomique et aux énergies alternatives
Minatec Campus | 17 rue des Martyrs | 38054 Grenoble Cedex | France
www.leti.fr
Thank you for your attention
Daivid.Fowler@cea.fr
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