Silicon-Based Waveguide Integrated Optical Phased Array Chips for LiDAR: Design Challenges and Breakthroughs (Invited)

Weihan Xu; Linjie Zhou; Jianping Chen

doi:10.3788/AOS241072

Acta Optica Sinica, Volume. 44, Issue 15, 1513026(2024)

Silicon-Based Waveguide Integrated Optical Phased Array Chips for LiDAR: Design Challenges and Breakthroughs (Invited)

Weihan Xu¹, Linjie Zhou^1,2, and Jianping Chen^1,2、*

¹State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, Shanghai 200240, China

²SJTU-Pinghu Institute of Intelligent Optoelectronics, Pinghu314200, Zhejiang, China

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Figures & Tables(14)

Fig. 1. Beamforming principle of OPA. (a) Far-field beam pattern of under-sampled array of $Λ_{x} = Λ_{y} = 2 λ_{0}$ ; (b) angle spectrum domain grating-lobe diagrams of OPA, $Λ_{x} = Λ_{y} = 0.5 λ_{0}$ (upper), $Λ_{x} = Λ_{y} = 0.75 λ_{0}$ (lower)

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Fig. 2. Several OPA optimization methods. (a) Spatial filtering through element design; (b) schematic diagram of superposition of interference pattern between paired array elements in a sparse array, only the beamforming direction enjoys the array gain; (c) amplitude distribution of one-dimensional array with windowing (left) and far-field intensity distribution shown in the zoy plane (right)

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Fig. 3. Coordinate systems and scanning behavior of phase-actuated 2-D beamsteering. (a)(b) Far-field coordinate systems and their transformations; (c) typical 2-D scanning performance over a large field of view

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Fig. 4. Structure diagram of OPA

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Fig. 5. Beamsteering actuated by wavelength tuning. (a) Principle of 1-D phased array assisted with wavelength tuning^[65]; (b) 2-D dispersive scanning with wavelength-dependent phase shift based on optical delay^[66]

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Fig. 6. Silicon-based hybrid-integrated ECL^[78]. (a) Device structure; (b) wavelength tuning performance

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Fig. 7. Wafer-bonding process flow for heterogenous integration of III-V on silicon^[83]

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Fig. 8. OPA integrated on the Si-Si₃N₄ multi-layered platform^[87]

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Table 1. Performance indicators of automotive LiDAR

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Table 1. Performance indicators of automotive LiDAR

Performance	LiDAR type	Nominal value	Notes
Maximum detectable range /m	Long-range	200-300	Target reflectivity≤10%, typical dynamic range≥70 dB
Maximum detectable range /m	Short-range	20-50	Target reflectivity≤10%
Ranging resolution /cm	Long-range	≤1/5	0~50 m/>50 m
Ranging resolution /cm	Short-range	≤1	0~50 m
Angular resolution /(°)	Long-range	≤0.1	In both horizontal and vertical directions, effective spot size ~50 cm@300 m
Angular resolution /(°)	Short-range	≤0.5	In both horizontal and vertical directions
Horizontal FOV /(°)	Long-range	120	i) Effective point-rate for long-range LiDARs>6.0×10⁶ s^-1, which is however, limited by the round-trip travelling time of photons at ranges beyond 100 m ii) Effective point-rate for short-range LiDARs>8.6×10⁵ s^-1, where dominant flash solutions are at about 2.0×10⁶ s^-1
Horizontal FOV /(°)	Short-range	120
Vertical FOV /(°)	Long-range	≥25
Vertical FOV /(°)	Short-range	≥70
Frame rate /Hz	Long-range	≥20
Frame rate /Hz	Short-range	≥20

Table 2. Latest development of OPAs under the architecture of 2-D dispersive arrays

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Table 2. Latest development of OPAs under the architecture of 2-D dispersive arrays

Year	Platform	Scale	Aperture area $x \times y / (μ m \times μ m)$	Beam divergence $Δ θ_{X} \times Δ θ_{Y} / [(°) \times (°)]$	$Θ_{X} \times Θ_{Y} / [(°) \times (°)]$ @tuned wavelength /nm
2020^［66］	SOI	32	800×500	0.11×0.2	35.8×5.5@200
2022^［72］	SOI	112	1500×160	0.2×1.8	6×10@40
2022^［74］	SiN	8^*×39	1000×234	0.18×0.36	11.2×12@35
2023^［76］	SiN	128	600×500	0.13×0.16	9.3×22.2@140
2024^［77］	SOI	128	3500×265	0.05×0.233	10.4×43.9@63.7

Table 3. Recent progress on OPAs integrated on the Si-Si₃N₄ multi-layered platform

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Table 3. Recent progress on OPAs integrated on the Si-Si₃N₄ multi-layered platform

Year	Scale	Aperture area $x \times y / (μ m \times μ m)$	Beam divergence $Δ θ_{X} \times Δ θ_{Y} / [(°) \times (°)]$	$Θ_{X} \times Θ_{Y}$ $/ [(°) \times (°)]$	Tuned wavelength /nm
2021^［88］	64	1500×160	0.075×0.69	22.7×35.5	Externally tuned 130
2021^［89］	128	3000×4000	0.1×0.02	19.2×140	Externally tuned 280*
2022^［90］	256	10300×1566	0.015×0.05	16×140 30×140	Internally tuned 100 Externally tuned 180
2022^［91］	256	3000×512	0.044×0.154	16.1×45.6	Externally tuned 150
2023^［92］	256	2500×1800	0.068×0.066	14.8×150	Externally tuned 200*

Table 4. Demonstrated beamforming performance for aliasing-suppressed aperiodic arrays
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Table 4. Demonstrated beamforming performance for aliasing-suppressed aperiodic arrays
Year Scale Average pitch / $λ_{0}$ Fill factor /% Beamforming loss /dB SLSR /dB
2021^［89］ 128 19.9 3.2 ~13 10
2022^［90］ 256 3.9 6.5 17 11
2023^［98］ 128 2.1 55 4.6 14
2023^［92］ 256 4.55 14.2 12.5 8.9

Table 5. Demonstrated aliasing suppression performance of bi-static vernier arrays
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Table 5. Demonstrated aliasing suppression performance of bi-static vernier arrays
Year Scale（TX/RX） TX pitch /μm RX pitch /μm $Θ_{X} \times Θ_{Y}$ / $[(°) \times (°)]$ SMSR /dB
2022^［101］ 32/31 16 16.516 NA 6.4
2022^［102］ 64/64 9.2 12.4 23×16.3 11.3
2024^［103］ 128/128 3.8 4.2 3×160 10.4~25.3

Table 6. Implementation status of LiDAR indicator requirements

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Table 6. Implementation status of LiDAR indicator requirements

Performance	OPA solution	Requirement
Performance	OPA solution	Long-range	Short-range
Maximum detectable range /m	100^［104］	200-300	20-50
Ranging resolution /cm	0.55^［103］	<1（0-50 m） <5（>50 m）	<1
Angular resolution /（°）	$Δ θ_{Y}$ is 0.01^［59］ $Δ θ_{X}$ is 0.008^［105］	<0.1	<0.5
Horizontal FOV /（°）	160^［103］	120-360	120
Vertical FOV /（°）	30^［87］	≥25	≥70
Frame rate /Hz	20^［106］	≥20	≥20
Point rate /s^-1	2.6×10^5［107］	6×10⁶ 5×10⁵@300 m	8.6×10⁵ >2.0×10⁶ s^-1 for flash solutions

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Weihan Xu, Linjie Zhou, Jianping Chen. Silicon-Based Waveguide Integrated Optical Phased Array Chips for LiDAR: Design Challenges and Breakthroughs (Invited)[J]. Acta Optica Sinica, 2024, 44(15): 1513026

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Paper Information

Category: Integrated Optics

Received: May. 27, 2024

Accepted: Jul. 9, 2024

Published Online: Jul. 31, 2024

The Author Email: Chen Jianping (jpchen62@sjtu.edu.cn)

DOI:10.3788/AOS241072

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Performance indicators of automotive LiDAR

Table 1. Performance indicators of automotive LiDAR

Table 2. Latest development of OPAs under the architecture of 2-D dispersive arrays

Table 2. Latest development of OPAs under the architecture of 2-D dispersive arrays

Table 3. Recent progress on OPAs integrated on the Si-Si3N4 multi-layered platform

Table 3. Recent progress on OPAs integrated on the Si-Si3N4 multi-layered platform

Table 4. Demonstrated beamforming performance for aliasing-suppressed aperiodic arrays

Table 4. Demonstrated beamforming performance for aliasing-suppressed aperiodic arrays

Table 5. Demonstrated aliasing suppression performance of bi-static vernier arrays

Table 5. Demonstrated aliasing suppression performance of bi-static vernier arrays

Table 6. Implementation status of LiDAR indicator requirements

Table 6. Implementation status of LiDAR indicator requirements

Table 3. Recent progress on OPAs integrated on the Si-Si₃N₄ multi-layered platform

Table 3. Recent progress on OPAs integrated on the Si-Si₃N₄ multi-layered platform