Silicon Diffraction Grating for Lidar Efficiency
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Solution Overview
Problem
Existing diffraction gratings face challenges in achieving high efficiency and low cost while maintaining performance across various wavelengths and angles of incidence.
Innovation Solution
The development of diffraction gratings with silicon substrates and grating lines that extend perpendicularly or with slight slopes, combined with anti-reflection coatings and etch stop layers, enhances efficiency and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diffraction grating manufacturing methods are used, then cost is reduced, but efficiency and uniformity deteriorate
Solution Approach 1:
The patent combines multiple functions into a single silicon substrate structure: the substrate serves as both the base material and the grating structure itself, with grating lines directly formed on the silicon surface. This integration eliminates the need for separate grating materials and reduces assembly steps, achieving high diffraction efficiency while lowering manufacturing cost through simplified production processes.
Solution Approach 2:
The patent optimizes specific parameters of the silicon grating structure, including grating line width (1-10 micrometers), spacing (10-100 micrometers), and depth (1-20 micrometers), to achieve peak diffraction efficiency at target wavelengths. By precisely controlling these geometric parameters during manufacturing, the patent achieves high efficiency without requiring complex post-processing, thereby reducing overall manufacturing cost.
2Reliability
If grating lines are made longer to improve diffraction efficiency, then manufacturing precision requirements worsen
Solution Approach 1:
The patent employs partial etching of the silicon substrate, creating grating lines with depths of 1-20 micrometers rather than penetrating through the entire substrate. This partial action approach achieves sufficient diffraction efficiency while maintaining manufacturability, as it avoids the extreme precision requirements associated with through-substrate etching and reduces sensitivity to minor variations in grating line dimensions.
Solution Approach 2:
The patent applies different structural characteristics to different regions of the grating: grating lines have specific depths and widths optimized for diffraction, while the spaces between lines maintain the bulk silicon properties. This local differentiation allows the grating lines to achieve high diffraction efficiency without requiring the entire substrate to meet stringent uniformity specifications, thereby relaxing overall manufacturing precision requirements.
3Reliability
If diffraction gratings are designed for specific wavelengths, then efficiency improves, but adaptability to other wavelengths worsens
Solution Approach 1:
The silicon-based diffraction grating is designed with geometric parameters that provide effective diffraction across a broad spectral range. By optimizing the grating period and line width ratios rather than targeting a single wavelength, the structure achieves useful diffraction efficiency from visible through infrared wavelengths, enabling a single grating to serve multiple wavelength applications without requiring redesign.
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
These diffraction gratings demonstrate high efficiency, with over 80% diffraction into the first order across a range of input angles, and are cost-effective due to optimized manufacturing processes.
Implementation Method 1
a plurality of grating lines extending from the silicon substrate to diffract light at one or more wavelengths
Implementation Method 2
anti-reflection coatings and etch stop layers
Data Source
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AI summary
Diffraction grating and method for manufacturing it. The diffraction grating has ridges of thickness of at least 1 micron and is made on a silicon substrate. It can further comprise: an anti-reflection coating on the ridges and on the other side of the substrate, an etch-stop layer between the substrate and the ridges. A preferred material is silicon nitrate. Applications for a lidar for an automated vehicle is also disclosed. In some embodiments, grating lines of the diffraction gratings may have several sub-lines that make up each grating line of the diffraction grating. The sub-lines may be sub-wavelength features. In some embodiments, several silicon diffraction gratings may be made from a wafer, such as a wafer with a diameter of 300 millimeters. The wafer may be etched precisely across the entire wafer, leading to a high yield of the diffraction gratings.