# US 2025/0085397 A1 · High contrast grating for highly reflective mems surface for lidar

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- Number: US 2025/0085397 A1
- Document ID: US20250085397A1
- Status: Published application
- Kind: A1
- Application number: 18/957,610
- Filed: 2024-11-22
- Published: 2025-03-13
- Earliest claimed: 2020-12-03
- Assignees: Beijing Voyager Technology Co., Ltd.
- Applicants: Beijing Voyager Technology Co., Ltd.
- Inventors: Yue Lu; Youmin Wang
- Web page: https://patentgrep.com/patent/US20250085397A1

## CPC

- G01S 7/481: Constructional features, e.g. arrangements of optical elements
- G02B 5/1809: {with pitch less than or comparable to the wavelength}
- G01S 7/4814: {of transmitters alone}
- G01S 7/4865: Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487)
- G01S 17/931: of land vehicles
- G02B 5/1857: {using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams}
- G02B 5/1861: {Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials (G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence)}
- G02B 7/1821: {for rotating or oscillating mirrors}
- G02B 26/0841: {the reflecting element being moved or deformed by electrostatic means}
- G02B 26/101: {with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129)}
- G01S 7/4817: {relating to scanning}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A grating for a steering mirror of a LiDAR system is made without a metal coating. The grating comprising a plurality of ridges defined by a period. The period has a width that is equal to or less than a wavelength of a laser of the LiDAR system. The ridges can be made of crystalline silicon to form a high-contrast grating.

## Claims

### Claim 1

A method for manufacturing a mirror for use in an autonomous vehicle using Light Detection and Ranging (LiDAR), the method comprising:
obtaining a semiconductor wafer, the semiconductor wafer comprising a device layer, a handle layer, and an insulting layer between the device layer and the handle layer;
applying a mask to define a pattern, wherein the pattern is configured to form a grating to reflect an optical beam defined by a center wavelength;
etching the device layer through the mask to form a plurality of ridges, wherein:
the plurality of ridges have walls defining a plurality of trenches between the plurality of ridges;
the plurality of ridges are defined by a period such that a width of one ridge plus a width of one trench is equal to a width of the period; and
the width of the period is less than the center wavelength;
removing a portion of the handle layer to form an opening in the handle layer; and
removing a portion of the insulating layer through the opening in the handle layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein etching the device layer through the mask is performed concurrently with etching a feature for a combdrive actuator.

### Claim 3 (depends on 1)

The method of claim 1, further comprising applying a metal layer to the semiconductor wafer before applying the mask.

### Claim 4 (depends on 1)

The method of claim 1, further comprising installing the grating in a LiDAR system as a reflector for a laser, wherein a metal coating does not cover a top surface of the grating.

### Claim 5 (depends on 1)

The method of claim 1, wherein the plurality of ridges are not covered by a metal.

### Claim 6 (depends on 1)

The method of claim 1, wherein the plurality of ridges are made of crystalline silicon.

### Claim 7 (depends on 1)

The method of claim 1, wherein:
the plurality of ridges are defined by a first refractive index;
the plurality of trenches are defined by a second refractive index; and
the first refractive index minus the second refractive index is equal to or greater than 2.