Asymmetric Waveguide Grating Antenna for Low-Crosstalk LiDAR
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Solution Overview
Problem
Waveguide grating antenna arrays in LiDAR devices suffer from optical crosstalk between antennas, which diminishes resolution, beam quality, and increases beam divergence, making it difficult to achieve focused and intense light output.
Innovation Solution
A WGA array design combining asymmetric ridge waveguides, extreme skin-depth waveguides, and Si/SiN dual-layer unidirectional structure with specific geometric parameters to reduce crosstalk and enhance unidirectional emission, featuring a lower waveguide layer with alternating silicon ridges and an upper layer of silicon nitride gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If waveguide grating antenna arrays are used to generate focused light output, then light intensity and focus are improved, but optical crosstalk between antennas increases
Solution Approach 1:
The patent employs asymmetric waveguide structures with different ridge widths and grating configurations to break the symmetry of optical mode coupling between adjacent antennas. This asymmetry reduces optical crosstalk by preventing coherent coupling while maintaining the focusing capability of each individual antenna, thus preserving light intensity without the harmful crosstalk effect.
Solution Approach 2:
The patent introduces a vertical dimension by stacking multiple waveguide layers with different materials (Si/SiN) and configurations. This three-dimensional structure enables independent control of optical modes in different layers, allowing focused light output while isolating adjacent antennas vertically to reduce lateral optical crosstalk.
2Reliability
If optical crosstalk is reduced to increase focus and intensity, then beam quality is improved, but device complexity increases
Solution Approach 1:
The patent divides the waveguide structure into multiple discrete layers with distinct functions: a first waveguide layer for light propagation and a second waveguide layer with gratings for beam steering. This segmentation allows independent optimization of each layer for crosstalk reduction while maintaining overall system simplicity through modular design.
Solution Approach 2:
The patent uses composite material structures combining silicon and silicon nitride waveguides with different optical properties. This composite approach enables tailored optical confinement and reduced crosstalk through material contrast while maintaining manufacturability through standard semiconductor fabrication processes.
3Object-generated harmful factors
If asymmetric waveguide structures are used to reduce crosstalk, then optical crosstalk suppression is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes specific geometric parameters such as ridge widths, grating periods, and layer thicknesses to achieve effective crosstalk suppression. By carefully selecting these parameters within manufacturable ranges, the design achieves asymmetric optical coupling reduction while remaining compatible with standard fabrication tolerances.
Solution Approach 2:
The patent implements asymmetric structures with moderate asymmetry rather than extreme asymmetry, achieving sufficient crosstalk suppression through partial asymmetry in ridge widths and grating configurations. This approach provides adequate performance improvement without pushing manufacturing precision to unrealistic levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves low optical crosstalk, high directionality, and balanced emission between waveguide antennas, resulting in improved beam steering, reduced beam divergence, and increased light intensity with a wide field of view, suitable for LiDAR applications.
Implementation Method 1
The SiN gratings may induce a constructive interference for unidirectional upward emissions
Implementation Method 2
asymmetric ridge waveguides, extreme skin-depth waveguides
Data Source
AI summary
A waveguide grating antenna apparatus includes a substrate layer, a lower waveguide array layer upon the substrate, and an upper waveguide array layer positioned above the lower waveguide array layer. The lower waveguide array layer is composed of a plurality of first waveguides extending axially and a plurality of second waveguides extending axially and arranged in parallel and alternating in position with the plurality of first waveguides across the lower waveguide array layer. Each first waveguide is of a first maximum width. Each second waveguide is of a second maximum width narrower than the first maximum width and is spaced apart from each adjacent first waveguide. The upper waveguide array layer is composed of adjacent, separated elements extending axially along each first waveguide and each second waveguide.