CN112859256A

CN112859256A - Grating coupler positioning measurement method based on image recognition

Info

Publication number: CN112859256A
Application number: CN202110018302.1A
Authority: CN
Inventors: 程振洲; 胡浩丰; 武靖雯; 邢正锟; 刘铁根
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2021-05-28
Anticipated expiration: 2041-01-07
Also published as: CN112859256B

Abstract

The invention discloses a method for positioning and measuring a grating coupler based on image recognition, which specifically includes the following steps: (1) locating the position coordinates of the grating coupler in a chip design drawing; (2) comparing the chip design drawing with the position of the chip on the measuring platform The size is mapped and matched, so as to obtain the position coordinates of the grating coupler in the chip on the measuring platform; (3) Use the program to control the movement of the stage to realize the micron-level positioning of the coupled fiber and the grating coupler; (4) Use spatial scanning The method realizes the positioning of the position of the coupling fiber and the grating coupler below 100 nanometers, and finds the optimal coupling position for chip measurement.

Description

Grating coupler positioning measurement method based on image recognition

Technical Field

The invention relates to the field of measurement of automatic coupling of optical fibers and photonic chips, in particular to a measurement method for positioning the position of a grating coupler based on image recognition and controlling the optical fibers to automatically find the optimal coupling position.

Background

The photonic chip not only has the advantages of high communication speed, electromagnetic interference resistance and the like, but also has the potential of realizing the monolithic integration of various devices, thereby having wide application prospect in the fields of Internet of things, artificial intelligence and the like. In recent years, the research and development and testing of photonic chips have attracted the attention of more and more researchers, and the coupling of optical fibers and chips is a very important chip packaging technology in the research and development and testing processes of photonic chips. If the coupling can be realized quickly, accurately and automatically, the labor and the time are undoubtedly saved, and the research and development and the test efficiency of the photonic chip are greatly improved. The couplers commonly used at present are wedge couplers, prism couplers, grating couplers and the like. Compared with other coupling methods, the grating coupler has the advantages of large alignment tolerance, no need of wafer or chip pretreatment, freer coupling position and the like, and therefore, the grating coupler plays a very important role in research, development and application of photonic chips.

A number of patents relating to the coupling of optical fibers and photonic chips have been reported. For example, a waveguide-optical fiber automatic core adjustment method and device based on a multi-target evolution algorithm, which are designed by Shanghai Richter university Chen snow and the like in 2007 (Chinese invention patent: 200710038988.0); an automatic control system for aligning and coupling an optical fiber and an electro-optical modulator, which is designed by Xuhaihua et al, semiconductor institute of Chinese academy of sciences in 2008, performs alignment by controlling the optical fiber to move and scan out a maximum power point (Chinese patent: 200810224107.9); the invention relates to a method for automatically positioning and placing optical fibers, which is invented by the 2016 Beijing aerospace university Lihuicheng et al, and the optical fibers are placed based on an image processing technology (Chinese invention patent: 201610270222.4); an optical fiber-waveguide automatic alignment coupler invented by Song Daizuan of Beijing aerospace university in 2018 based on image processing is used for determining the position of an output point by an image processing method (Chinese invention patent: 201810397010.1). However, for the grating coupler, there is no method that can automatically position the grating coupler, move the optical fiber to the grating coupler, and find the optimal coupling position for device testing.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a grating coupler positioning and measuring method based on image recognition.

The purpose of the invention is realized by the following technical scheme:

a grating coupler positioning measurement method based on image recognition specifically comprises the following steps:

(1) positioning the position coordinates of the grating coupler in the chip design drawing;

(2) mapping and matching the chip design drawing with the size of a chip on a measuring platform to obtain a position coordinate of a grating coupler in the chip on the measuring platform;

(3) the displacement table is controlled to move by a program, so that micron-scale positioning of the positions of the coupling optical fiber and the grating coupler is realized;

(4) and the space scanning method is used for realizing the positioning of the coupling fiber and the grating coupler below the hundred nanometers, and finding out the optimal coupling position for chip measurement.

Further, the positioning of the position coordinates of the grating coupler in step (1) can be performed by extracting the relevant layer of the grating coupler from the GDS file of the chip design drawing, and then positioning the grating coupler by using an image recognition method to find the position coordinates of the grating coupler.

Further, in the step (2), the chip design drawing and the chip on the measuring platform are subjected to size mapping matching, and position information of the GDS file of the chip design drawing and the position information of the plurality of markers on the chip can be respectively obtained by adopting an image recognition method, so that the position coordinates of the grating coupler on the measuring platform are obtained.

Further, the step (3) uses a program to control the movement of the displacement table to control the movement of the coupling optical fiber or to control the movement of the chip on the chip measuring platform.

Further, the spatial scanning method in the step (4) scans all positions in a certain area point by point with the precision of less than hundred nanometers, and can record and compare the coupling efficiency, or the coupling spectral bandwidth, or the coupling reflection power of the grating coupler under each position coordinate; the position with the highest coupling efficiency, or the maximum coupling spectral bandwidth, or the minimum coupling reflected power is obtained correspondingly, namely the optimal coupling position.

The invention also provides an image recognition-based grating coupler which comprises an optical fiber displacement table, a chip displacement table, a camera and a motor, wherein the optical fiber displacement table is arranged on two sides above the chip displacement table, the chip displacement table is used for fixing a chip, the optical fiber displacement table is used for fixing an optical fiber, the optical fiber is coupled with the chip in a near-vertical coupling mode, and the optical fiber displacement table and the chip displacement table are both controlled by the motor; grating couplers are designed on two sides of the waveguide in the chip, and three cross-shaped marks are designed in the chip; the camera is fixed right above the chip and used for collecting images of the chip.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. the invention has the advantage of wide applicability. The method determines the coupling position according to the GDS file of the chip design diagram, is suitable for the production test of wafer level (wafer level) and the research and development of chip level (die level), and is efficient and flexible.

2. The invention utilizes the image recognition method to quickly position the general position of the grating coupler, and then utilizes the space scanning method to accurately scan out the optimal coupling position, and the coupling process has the advantages of quickness and accuracy.

3. The invention is a low-cost chip positioning measurement method, and the measurement method is based on the improvement of the conventional common photonic chip measurement system, and the change of hardware is small.

4. The invention has the advantage of high automation degree, can realize the coupling of full-automatic chip devices by optimizing the algorithm aiming at the structural characteristics of different waveguide devices, and reduces the manual test cost.

5. The invention is a coupling method combining hardware and algorithm, the coupling efficiency and speed can be improved by upgrading the algorithm, and the system has the advantage of later upgradability.

Drawings

Fig. 1 is a hardware diagram of an embodiment of a grating positioning and automatic coupling measurement method.

FIG. 2 is a hardware diagram of an embodiment of a grating positioning and automatic coupling measurement method.

Fig. 3 is a flow chart of the automatic coupling measurement of the grating positioning and automatic coupling measurement method.

FIG. 4 is a flow chart of grating positioning and automatic coupling measurement method.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 1 shows an embodiment of the present invention, in which an optical fiber 1 is fixed on an optical fiber displacement stage 3, and is coupled with a chip 5 in a near-vertical coupling manner, the chip 5 is fixed on a chip displacement stage 4, and the optical fiber displacement stage 3 and the chip displacement stage 4 are both controlled by a motor 8. Grating couplers 6 are designed in the chip 5 on both sides of the waveguide, while three cross-shaped markings 7 are designed in the chip. The camera 2 is responsible for capturing images of the chip 5. The physical diagram of the hardware of the specific embodiment is shown in FIG. 2.

The implementation flow of the specific embodiment is shown in fig. 3, after the chip 5 is fixed on the measurement platform, firstly, the chip design drawing is subjected to image processing to obtain the coordinates of the grating coupler 6 on the chip design drawing, then, the camera 2 is matched with the movement of the chip displacement table 4 to acquire the actual image of the chip 5, and the actual image and the chip design drawing are subjected to image processing and are matched with each other to obtain the coordinates of the chip 5 on the measurement platform. And then combining the coordinates of the grating coupler 6 on the chip design drawing with the coordinates of the chip 5 on the measuring platform to obtain the coordinates of the grating coupler 6 on the measuring platform. Next, after moving the optical fiber 1 to the micron-scale position of the grating coupler 6, performing spatial scanning to obtain an optimal coupling position with the precision below the hundred nanometers: the power and wavelength of input light are fixed, the optical fiber 1 is controlled to scan point by point along a certain path, the output power of each point is compared to obtain the position with the highest output power, namely the optimal coupling position, and the optimal coupling position is determined and then the measurement can be carried out.

Fig. 4 shows a specific flow of a grating coupler positioning method. In a first step, the coordinates of the grating coupler 6 on the chip design are determined. Converting an input chip design drawing into a gray level image, scanning the image line by line, finding out a region of each line of gray level change spatial frequency within a set threshold value, recording start and stop x-direction coordinates of the region, comparing results of each line, recording y-direction coordinates corresponding to the lines if regions with grating couplers exist in the same x-coordinate position in each line or every few lines in a certain number of continuous lines, positioning the regions with the grating couplers through the coordinates, screening according to the area size of the regions, wherein the rest regions are regions where the grating couplers 6 are located, and taking midpoint coordinates of the regions, namely coordinates of the grating couplers 6 on the chip design drawing.

Secondly, determining the coordinates of the chip 5 on the measuring platform: three marks 7 for determining positions are designed on the chip 5 in advance, edge processing and contour extraction are carried out on the binary image of the chip design drawing, and then the shape of the extraction guide is screened according to parameters such as preset area, length-width ratio and the like, so that the marks 7 are found out, and the coordinates of the marks 7 on the chip design drawing are obtained. Then, the chip displacement table 4 is moved, the camera 2 is matched to shoot the chip 5 on the measuring platform comprehensively, a series of pictures obtained by shooting are subjected to the same image processing, a picture with a mark 7 is found, and the coordinate of the mark 7 relative to the measuring platform is determined through the displacement of the chip displacement table 4 relative to the initial position and the position of the mark 7 on the picture when the picture is shot. After the coordinates of the three marks 7 relative to the measuring platform are obtained respectively, the coordinates are matched with the coordinates of the marks 7 relative to the chip design drawing, and accordingly the coordinates of the chip 5 on the measuring platform are obtained.

And thirdly, calculating and finding the coordinates of the grating coupler 6 on the measuring platform. And combining and comparing the coordinates of the grating coupler 6 on the chip design drawing obtained in the first two steps with the coordinates of the chip 5 on the measuring platform, and calculating the coordinates of the grating coupler 6 on the measuring platform, thereby finishing the positioning process of the grating coupler 6.

The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. a grating coupler positioning measurement method based on image recognition, is characterized in that, specifically comprises the following steps:

(1) Position the position coordinates of the grating coupler in the chip design drawing;

(2) Mapping and matching the chip design drawing and the size of the chip on the measuring platform to obtain the position coordinates of the grating coupler in the chip on the measuring platform;

(3) Using the program to control the movement of the displacement stage to realize the micron-level positioning of the position of the coupled optical fiber and the grating coupler;

(4) Use the spatial scanning method to realize the positioning of the position of the coupling fiber and the grating coupler below 100 nanometers, and find the optimal coupling position for chip measurement.

2. a kind of grating coupler positioning measurement method based on image recognition according to claim 1, is characterized in that, the positional coordinates of positioning grating coupler described in step (1) can be adopted in chip design drawing GDS file Extract the relevant layers of the grating coupler, and then use the method of image recognition to locate the grating coupler to find the position coordinates of the grating coupler.

3. a kind of grating coupler positioning measurement method based on image recognition according to claim 1, is characterized in that, in step (2), the size mapping matching of chip design drawing and chip on the measuring platform can adopt image recognition method. Methods The GDS file of the chip design drawing and the position information of several markers on the chip were obtained respectively, so as to obtain the position coordinates of the grating coupler on the measuring platform.

4. a kind of grating coupler positioning measurement method based on image recognition according to claim 1, is characterized in that, utilizes the program-controlled displacement stage to move in step (3) to control the movement of coupling optical fiber or on the control chip measurement platform chip movement.

5. a kind of grating coupler positioning measurement method based on image recognition according to claim 1, is characterized in that, in step (4), the method of spatial scanning is to scan in a certain area point by point with the precision below 100 nanometers. All positions, and can record and compare the coupling efficiency, or coupling spectral bandwidth, or coupling reflected power of the grating coupler at each position coordinate; correspondingly obtain the one with the highest coupling efficiency, or the largest coupling spectral bandwidth, or the smallest coupling reflected power position, that is, the optimal coupling position.