Laser antireflection film designing method for film layer with non-uniform refractive index

Abstract

The invention belongs to the technical field of vacuum film plating, and particularly to a designing method for an antireflection film for laser wavelength. The method comprises the following steps: 1) measuring refractive indexes of an H layer and an L layer through an ellipsometer; 2) computing physical thicknesses of the H layer and the L layer on an ideal setting condition; 3) setting the physical thickness space of the H layer to [(1-absolute value of (deltaH))dH,(1+absolute value of(deltaH)dH), and setting the physical thickness space of the L layer to [(1-absolute value of (deltaL)dL,(1+absolute value of (deltaL)Dl); 4) performing uniform layering on the H layer and the L layer; 5) discretizing the refractive indexes of an H layer and an L layer according to a preset layer number; 6) matrixing the thickness spaces of the H layer and the L layer, determining a step length according to control precision of depositing equipment, and computing residual refractive indexes in the physical thickness spaces; and 7) searching and determining a minimum point of the residual refractive indexes in a physical thickness matrix space, wherein the physical thickness layers of the corresponding H layer and the L layer are designed results.

Description

technical field [0001] The invention belongs to the technical field of vacuum coating, and in particular relates to a design method of a laser anti-reflection film. Background technique [0002] The single-wavelength anti-reflection coating used in laser systems generally adopts a structure with two layers of high and low refractive index materials with matching optical thickness. If the remaining reflectance of the anti-reflective coating is controlled below 0.01%, that is, when the transmittance reaches above 99.99%, ion beam sputtering deposition technology is generally used. The optical thin film prepared by this technology has the advantages of small absorption, small scattering of the film layer, high density, and improved surface roughness of the substrate, and is widely used in the preparation of laser thin films. [0003] However, the non-uniformity of the refractive index of the film prepared based on the ion beam sputtering deposition method is relatively obvious...

AI Technical Summary

Problems solved by technology

[0003] However, the non-uniformity of the refractive index of the film prepared based on the ion beam sputtering deposition method is relatively obvious, and the optical film grown under the non-equilibrium physical process generally has a certain degree of non-uniformity of the refractive index in the thickness growth direction. The size of non-uniformity is closely related to the deposition method, deposition process parameters, and surface properties of the substrate

Although the non-uniformity of the refractive index can be minimized during the process, it cannot be completely eliminated. The non-uniformity of the refractive index of the film directly affects the spectral performance of the film.

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