CN-115826116-B - Preparation method of two-dimensional beam-splitting diffraction grating for realizing specific dot pattern

CN115826116BCN 115826116 BCN115826116 BCN 115826116BCN-115826116-B

Abstract

The invention discloses a preparation method of a two-dimensional beam splitting diffraction grating for realizing a specific dot pattern, which respectively constructs a first cost function cost_x and a second cost function cost_y according to diffraction orders of a spot array actually required in an x-y direction and diffraction order uniformity errors, respectively obtains phase change point space modulation coordinates after optimization in the x-y direction by minimizing the first cost function cost_x and the second cost function cost_y, carries out orthogonal multiplication and expansion on the phase change point space modulation coordinates after optimization in the x-y direction to obtain orthogonal two-dimensional diffraction grating structure parameters, processes the orthogonal two-dimensional grating structure through at least one pattern transformation mode to obtain final two-dimensional diffraction grating structure parameters and etching depth, generates a photoetching mask, and carries out micro-nano processing on a substrate according to the photoetching mask to obtain a two-dimensional beam splitting diffraction grating element.

Inventors

WU CHENYANG
HUANG XUANLUN
WANG JIAXING

Assignees

深圳博升光电科技有限公司

Dates

Publication Date: 20260505
Application Date: 20220929

Claims (6)

1. The preparation method of the two-dimensional beam-splitting diffraction grating for realizing the specific dot pattern is characterized by comprising the following steps of: according to respectively Diffraction orders of the spot array actually required by the direction are combined with diffraction efficiency and diffraction order uniformity errors to construct a first cost function Second cost function ; By minimizing the first cost function respectively Second cost function Obtaining The phase change point after the optimization in the y direction spatially modulates the coordinates; For the said 、 Orthogonal multiplication and expansion are carried out on the phase change point space modulation coordinates after direction optimization, and orthogonal two-dimensional diffraction grating structure parameters are obtained; Processing the orthogonal two-dimensional grating structure in at least one pattern transformation mode to obtain final two-dimensional diffraction grating structure parameters and etching depth, and generating a photoetching mask; micro-nano processing is carried out on the substrate according to the photoetching mask plate, and a two-dimensional beam splitting diffraction grating element is obtained; by minimizing the first cost function respectively Second cost function Obtaining The phase change point space modulation coordinates after the optimization in the y direction are specifically that a computer iterative optimization algorithm is adopted to minimize the first cost function Second cost function Obtaining The phase change point space after the y direction optimization modulates the coordinates, and the computer iterative optimization algorithm comprises a simulated annealing iterative optimization algorithm and a gradient descent iterative optimization algorithm; The pair of the 、 Orthogonal multiplication and expansion are carried out on the phase change point space modulation coordinates after direction optimization to obtain orthogonal two-dimensional diffraction grating structure parameters, specifically, the phase change point space modulation coordinates are obtained through optimization Direction and direction Phase change point spatial modulation coordinate determination after direction optimization 、 A directional one-dimensional grating structure, after which the said Direction and direction The direction one-dimensional grating is unfolded in the orthogonal direction, and an orthogonal two-dimensional grating structure is obtained; The graphic transformation mode comprises miscut transformation, rotation transformation and graphic splicing.
2. The method for preparing a two-dimensional beam-splitting diffraction grating for realizing a specific dot pattern according to claim 1, wherein the simulated annealing iterative optimization algorithm minimizes the first cost function Obtaining The phase change point space modulation coordinates after direction optimization are specifically as follows: Setting an initial temperature Randomly generating initial solution of spatial modulation coordinates of normalized phase change point In the range of Obtaining a first cost function ; Each is provided with Number of iterations of a value Order-making Wherein , Indicating the rate of temperature decrease; For the current solution Applying random perturbation, generating new solutions in its neighborhood: ; determining new solution cost function values Increment of objective function value ; If the objective function value is increased Then accept As a new current solution, otherwise, with probability Judging whether to accept or not As a new current solution; At the temperature of Repeating the steps Performing the steps of secondary disturbance and acceptance; Judging the temperature Whether the termination temperature level is reached, if so, terminating the algorithm to obtain Space modulation coordinates of the phase change point after optimization in the direction, otherwise, returning to the current solution The iterative process is repeated with random perturbations applied.
3. The method for preparing a two-dimensional beam-splitting diffraction grating for realizing a specific dot pattern according to claim 2, wherein the simulated annealing iterative optimization algorithm minimizes the second cost function Obtaining The phase change point space modulation coordinates after direction optimization are specifically as follows: Setting an initial temperature Randomly generating initial solution of spatial modulation coordinates of normalized phase change point In the range of Obtaining a first cost function ; Each is provided with Number of iterations of a value Order-making Wherein , Indicating the rate of temperature decrease; For the current solution Applying random perturbation, generating new solutions in its neighborhood: ; determining new solution cost function values Increment of objective function value ; If the objective function value is increased Then accept As a new current solution, otherwise, with probability Judging whether to accept or not As a new current solution; At the temperature of Repeating the steps Performing the steps of secondary disturbance and acceptance; Judging the temperature Whether the termination temperature level is reached, if so, terminating the algorithm to obtain Space modulation coordinates of the phase change point after optimization in the direction, otherwise, returning to the current solution The iterative process is repeated with random perturbations applied.
4. The method for preparing a two-dimensional beam-splitting diffraction grating for realizing a specific dot pattern according to claim 3, wherein the orthogonal two-dimensional grating structure is processed by the shear-shift method to obtain final two-dimensional diffraction grating structure parameters and etching depth, specifically, in the horizontal direction, the directional distance from each point of the orthogonal two-dimensional grating structure to a certain straight line parallel to the direction is shear-shifted by 30 degrees in proportion to obtain the final two-dimensional diffraction grating structure, and the final two-dimensional diffraction grating structure parameters and etching depth are determined according to the final two-dimensional diffraction grating structure.
5. The method for preparing the two-dimensional beam-splitting diffraction grating for realizing the specific dot pattern according to claim 4, wherein the orthogonal two-dimensional grating structure is processed in the rotation transformation mode and the image splicing mode to obtain final two-dimensional diffraction grating structure parameters and etching depth, specifically, the orthogonal two-dimensional diffraction grating is subjected to the maximization of 0 to +/-2 diffraction order far-field light intensity in the x direction, the rotation transformation is respectively carried out clockwise by 0 degrees and 90 degrees, the final two-dimensional diffraction grating structure is finally obtained through pattern splicing, and the final two-dimensional diffraction grating structure parameters and etching depth are determined according to the final two-dimensional diffraction grating structure.
6. The method for preparing the two-dimensional beam-splitting diffraction grating for realizing the specific dot pattern according to claim 5, wherein the orthogonal two-dimensional grating structure is processed in the rotation transformation mode and the image splicing mode to obtain final two-dimensional diffraction grating structure parameters and etching depth, specifically, the orthogonal two-dimensional diffraction grating is subjected to the maximization of 0 to +/-2 diffraction order far-field light intensity in an x-direction target, the rotation transformation is respectively carried out clockwise by 0 degree, 45 degree and 90 degree, the final two-dimensional diffraction grating structure is finally obtained through pattern splicing, and the final two-dimensional diffraction grating structure parameters and etching depth are determined according to the final two-dimensional diffraction grating structure.

Description

Preparation method of two-dimensional beam-splitting diffraction grating for realizing specific dot pattern Technical Field The invention belongs to the technical field of optics, and particularly relates to a preparation method of a two-dimensional beam-splitting diffraction grating for realizing a specific dot pattern. Background An optical array generator is a device capable of dividing an incident laser beam into an emergent beam array with specific power distribution, and in various optical array generators, a Dammann grating realizes a laser far-field multistage spectrum point equal-intensity light spot array through the modulation of the space coordinate position of a binary optical phase change point. In the early 70 th century, dammann et al put forward the concept of Dammann grating in the process of researching a plurality of images to copy, and introduce a large-scale integrated circuit technology into the optical field for the first time, which lays a foundation for the development of micro-nano optics, the Dammann grating can enable incident monochromatic light to be efficiently converted into a lattice with equal light intensity distribution at a far field, and the advantages of simple design structure, mature manufacturing process, no need of accurate alignment and the like are presented. In recent years, great attention has been paid to the great potential in the fields of face recognition, three-dimensional imaging, structured light projection, optical communication and light calculation, VR (virtual reality)/AR (augmented reality), and the like. When the traditional Dammann grating is designed, a one-dimensional grating structure is determined by optimizing the spatial modulation coordinates of phase change points, then a two-dimensional grating structure is obtained by expanding the one-dimensional grating in the orthogonal direction, only axisymmetric equidistant diffraction lattice patterns, such as square lattices, round lattices and the like, can be realized in a far field, but other specific forms of lattice patterns, such as non-axisymmetric diffraction lattice patterns, unequal-interval diffraction lattice patterns, bar diffraction lattice patterns, non-square lattice patterns and the like, can not be realized, and the application of the Dammann grating in specific fields, such as non-central symmetric lattices, specific diffraction order maximization diffraction lattice pattern feature patterns and the like, such as three-dimensional measurement, laser cutting, laser scanning and the like, is greatly limited. The method is mainly based on the diffraction optical principle, and according to the expected target dot pattern, phase information required by the diffraction optical element is obtained through optimization of an iterative algorithm (such as Gerchberg-Saxton algorithm, gradient descent algorithm and the like) so as to obtain etching information of the diffraction optical element, but the method can generate stray light interference in a far field, has serious background noise and lower diffraction efficiency, can only design a super-surface structure by increasing the etching order of the diffraction optical element or using an electron beam lithography technology, further improves diffraction efficiency, greatly increases processing difficulty, processing uncertainty and processing cost, and is unfavorable for industrialized replication and mass production of the diffraction optical element. Disclosure of Invention Accordingly, a primary object of the present invention is to provide a method for preparing a two-dimensional beam-splitting diffraction grating for realizing a specific dot pattern. In order to achieve the above purpose, the technical scheme of the invention is realized as follows: The embodiment of the invention provides a preparation method of a two-dimensional beam-splitting diffraction grating for realizing a specific dot pattern, which comprises the following steps: respectively constructing a first cost function cost_x and a second cost function cost_y according to diffraction orders of the spot array actually required in the x and y directions and combining diffraction efficiency and diffraction order uniformity errors; obtaining phase change point space modulation coordinates after optimization in the x and y directions by minimizing the first cost function cost_x and the second cost function cost_y respectively; Orthogonal multiplication and expansion are carried out on the phase change point space modulation coordinates after the optimization in the x-direction and the y-direction, so that orthogonal two-dimensional diffraction grating structure parameters are obtained; Processing the orthogonal two-dimensional grating structure in at least one pattern transformation mode to obtain final two-dimensional diffraction grating structure parameters and etching depth, and generating a photoetching mask; and carrying out micro-nano processing on the substr