CN-122018152-A - Design method of long-wave infrared achromatic differential beam focusing type super-structured lens

CN122018152ACN 122018152 ACN122018152 ACN 122018152ACN-122018152-A

Abstract

The invention relates to the technical field of optical device design, in particular to a design method of a long-wave infrared achromatic differential beam focusing type super-structure lens. The method comprises the steps of determining substrate materials, nanostructure materials, radius R, focal length f and focal coordinates of four polarized channels, constructing a linear polarization unit phase parameter library and a transmissivity parameter library by FDTD scanning, performing achromatic phase optimization on four polarized states in a characteristic wavelength set based on a PSO algorithm to generate structural parameter distribution data of a linear polarization part and a circular polarization part, constructing an ultra-structure lens by row staggered arrangement, and verifying focusing performance of an ultra-structure lens array by an angular spectrum propagation algorithm. According to the invention, nanometer units for regulating and controlling linear polarized light and circular polarized light are integrated through row staggered arrangement, and achromatic phase cooperative optimization of a PSO algorithm is combined, so that multi-polarization-state beam splitting and focusing integrated integration is realized, the working wave band is widened, the broadband focusing consistency is improved, and the design and calculation cost of the super-structure lens array is reduced.

Inventors

FU QIANG
Ming Kun
WANG XIHANG
LIU ZIXIAN
WANG JIE
LI GUANHAI
JIANG HUILIN

Assignees

长春理工大学

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (10)

1. The design method of the long-wave infrared achromatic differential beam focusing type super-structured lens is characterized by comprising the following steps of: determining the substrate material, the nanostructure material and the focal coordinates of the radius R, the focal length f and four polarization channels of the super-structure lens; utilizing FDTD software to sweep the super-structure lens unit to construct a linear polarization unit phase parameter library And a transmittance parameter library ; Based on particle swarm optimization PSO algorithm, achromatic phase optimization is carried out on four polarization states in a characteristic wavelength set, and linear polarization part structural parameter distribution data are generated Structural parameter distribution data of circularly polarized parts ; In order to integrate units for respectively regulating and controlling linear polarized light and circular polarized light in the same device plane, a final super-structure lens structure is constructed by adopting a line staggered arrangement mode, wherein the lines with odd line numbers adopt the structural parameter distribution data of the linear polarization part The lines with even number adopt the structural parameter distribution data of the circular polarization part 。
2. The method of claim 1, wherein focal coordinates of the four polarization channels are respectively (-R/2, R/2), (-R/2 ), and (R/2, -R/2) in a focal plane, wherein R is a super-lens radius, the focal plane is located at z=f, and f is a focal length.
3. The method for designing a long-wave infrared achromatic differential beam focusing type super-structured lens according to claim 1, wherein the focal length f is determined by establishing a candidate focal length set, calculating ideal phase distribution corresponding to each candidate focal length in the candidate focal length set based on a Fresnel diffraction integral formula, using a Style ratio and focusing efficiency as evaluation indexes, and selecting a focal length with the largest Style ratio and the focusing efficiency meeting the requirement as a final design focal length.
4. The method for designing a long-wave infrared achromatic differential beam focusing type super-structure lens according to claim 1, wherein said scanning the super-structure lens unit by using FDTD software comprises: Determining that the unit shape is an elliptic cylinder, a cuboid or a cross rectangular structure and a structural parameter vector G, wherein: For an elliptic cylinder unit, g= (R 1 ,R 2 );R 1 is the major axis radius, R 2 is the minor axis radius; For a cuboid unit, g= (L x ,L y );L x is length in x-direction, L y is length in y-direction; For a cross rectangular unit, g= (L 1 ,W 1 ,L 2 ,W 2 );L 1 ,W 1 is the length and width of the first rectangular beam, respectively, and L 2 ,W 2 is the length and width of the second rectangular beam, respectively.
5. The method for designing a long-wave infrared achromatic differential beam focusing type super-structure lens according to claim 1, wherein parameters based on particle swarm optimization PSO algorithm are set to 100 population sizes, 150 iteration times, 1.49445 for both learning factors and 1.49445 for particle velocity variation range The particle position change range is 。
6. The method of designing a long-wave infrared achromatic differential beam focusing type super-structure lens according to claim 1, wherein said achromatic phase optimization includes: for the linear polarization part, based on the linear polarization unit phase parameter library And a transmittance parameter library The optimal additional phase under each characteristic wavelength is obtained by constructing an objective function of a phase error term and a transmissivity penalty term, so that broadband achromatic focusing of the linear polarization channel is realized; for the circularly polarized part, the linear polarization unit phase parameter library is firstly based on And a transmittance parameter library Constructing a unit phase parameter library corresponding to the circular polarization part And a transmittance parameter library And then, based on the constructed circular polarization unit phase parameter library and the transmissivity parameter library, solving to obtain the optimal additional phase under each characteristic wavelength by constructing an objective function of a phase error term and a transmissivity penalty term, thereby realizing broadband achromatic focusing of the circular polarization channel.
7. The method for designing a long-wave infrared achromatic differential beam focusing type super-structure lens according to claim 1, wherein the row staggered arrangement mode is as follows: Taking the geometric center of the super-structure lens as the origin of coordinates, wherein the plane of the super-structure lens is z=0, and the unit arrays are symmetrically distributed in the plane; Sequentially numbering the unit rows from top to bottom along the positive direction of the y axis, wherein the unit row closest to the edge of the +y direction is numbered as the 1 st row, and then the adjacent rows are sequentially numbered as the 2 nd row and the 3 rd row until the serial number is the N th row; the odd-numbered lines adopt preset linear polarization part structural parameter distribution data The lines with even number adopt preset circular polarization part structural parameter distribution data 。
8. The method of claim 1, further comprising verifying the focusing performance of the super-resolution lens by using an angular spectrum propagation algorithm, wherein the verifying comprises constructing an equivalent complex amplitude transmission function of the super-resolution lens, performing frequency domain truncation based on the Nyquist sampling theorem, and reconstructing a focal plane light field by two-dimensional Fourier transform and inverse Fourier transform.
9. The method for designing a long-wave infrared achromatic beam focusing type super-structure lens according to claim 8, wherein the step of verifying comprises: Determining splicing parameters of the super-structure lens array; constructing a complex amplitude transmission function of the super-structure lens array; free space focusing simulation and performance evaluation based on an angular spectrum propagation algorithm.
10. The method for designing a long-wave infrared achromatic differential beam focusing type super-structure lens according to claim 9, wherein determining the splicing parameters of the super-structure lens array comprises setting the effective caliber of a single beam splitting focusing type super-structure lens as D and the width of a splicing gap between adjacent sub-lenses as g, and the array splicing period is as follows: ; the effective imaging surface size of the detector is set as The number of splices along the x and y directions is: ; thereby obtaining an ultra-structured lens array covering the effective imaging surface of the detector.

Description

Design method of long-wave infrared achromatic differential beam focusing type super-structured lens Technical Field The invention relates to the technical field of optical device design, in particular to a design method of a long-wave infrared achromatic differential beam focusing type super-structure lens. Background In a long-wave infrared band (for example, 8.4-11.6 mu m), the polarization imaging can be used for scene applications such as target detection and material identification. Existing polarized imaging systems typically employ a combination of polarizing beam splitter devices and separate optical elements such as imaging lenses (or array lenses) to achieve detection of multiple polarization channels. However, the discrete component scheme may have the problems of larger volume, higher weight and the like during system integration, and is limited in application scenes with higher requirements on miniaturization and high integration level, such as airborne, satellite-borne and the like. In order to achieve miniaturization of the system, it is proposed to integrate beam splitting and focusing functions into a single-layer device by using a super-structured surface, thereby forming a beam splitting and focusing integrated device. In the existing implementation manner of the beam splitting focusing super-structure lens, common schemes comprise beam splitting and focusing of different polarization states through sub-pixel division, functional area splicing or multi-layer cascading and other modes. Under the condition that the size of the device is further reduced or the number of polarization channels is increased, the problems of reduced effective caliber utilization rate, reduced focusing efficiency and the like may be caused by the mode, so that the further miniaturization and high integration application of the device are not facilitated. In addition, the super-structured surface phase response usually has a certain dispersion characteristic, and focal shift may occur in a long-wave infrared broadband range, so that the device is easier to obtain better performance under the single-wavelength or narrower bandwidth condition, and the focusing performance under the broadband detection condition is limited to a certain extent. Therefore, it is desirable to provide a super-structured lens design scheme for a long-wave infrared broadband range, which can realize multi-polarization beam splitting and focusing, reduce the influence of chromatic aberration, and simultaneously have an extensible design and verification process. Disclosure of Invention In view of the above, the invention provides a design method of a long-wave infrared achromatic differential beam focusing type super-structure lens, which aims to improve the conditions of large volume, large mass and narrow working band of the existing long-wave infrared polarization imaging device. In order to achieve the above purpose, the present invention adopts the following technical scheme: in a first aspect, the present invention provides a method for designing a long-wave infrared achromatic differential beam focusing type super-structured lens, comprising the steps of: determining the substrate material, the nanostructure material and the focal coordinates of the radius R, the focal length f and four polarization channels of the super-structure lens; utilizing FDTD software to sweep the super-structure lens unit to construct a linear polarization unit phase parameter library And a transmittance parameter library; Based on particle swarm optimization PSO algorithm, achromatic phase optimization is carried out on four polarization states in a characteristic wavelength set, and linear polarization part structural parameter distribution data are generatedStructural parameter distribution data of circularly polarized parts; In order to integrate units for respectively regulating and controlling linear polarized light and circular polarized light in the same device plane, a final super-structure lens structure is constructed by adopting a line staggered arrangement mode, wherein the lines with odd line numbers adopt the structural parameter distribution data of the linear polarization partThe lines with even number adopt the structural parameter distribution data of the circular polarization part。 In a specific embodiment, the focal coordinates of the four polarization channels are taken as (-R/2, R/2), (-R/2 ), and (R/2, -R/2), respectively, in a focal plane, where R is the super-lens radius, the focal plane is at z=f, and f is the focal length. In a specific implementation, the focal length f is determined by establishing a candidate focal length set, calculating an ideal phase distribution corresponding to each candidate focal length in the candidate focal length set based on a Fresnel diffraction integral formula, and selecting a focal length with the maximum Style ratio and the required focusing efficiency as a final design focal length by using t