Refractive index tunable film structure and preparation method thereof

Abstract

The invention discloses a refractive index tunable film structure and a preparation method thereof. The refractive index tunable film structure is formed by etching a periodic microstructure on the surface of a single-layer film, the structure of the refractive index tunable film structure sequentially comprises a compact film layer and a periodic microstructure film layer from bottom to top, therefractive index of the compact film layer is equal to the refractive index of a film material, and the refractive index of the periodic microstructure film layer is related to microstructure parameters. The surface microstructure is equivalent to a dielectric layer with the refraction coefficient changing continuously, the equivalent refraction coefficient of the dielectric layer is smaller thanthe refractive index of the thin film material, and the overall refractive index of the thin film can be regulated and controlled by regulating and controlling the equivalent refractive index of the dielectric layer. The preparation method comprises the following steps: (1) plating a film on the substrate surface; (2) cleaning a film surface, and spin-coating photoresist on the film surface; (3) exposing the sample by adopting double-beam interference; (4) developing to obtain a required mask pattern; (5) transferring the mask pattern to the film by adopting a reactive ion beam etching technology; and (6) cleaning residues generated by etching. The proportion of air in the film is controlled by regulating and controlling the height and the duty ratio of the nano microstructure in the film,so that the refractive index of the film material can be regulated and controlled. The method has an extremely wide refractive index regulation and control range (from the refractive index of the airlayer to the refractive index of the film material), and is simple in process and high in repeatability.

Description

technical field [0001] The invention belongs to the field of optical thin films, and in particular relates to a thin film structure with adjustable refractive index and a preparation method thereof. Background technique [0002] After more than two hundred years of development, optical thin film technology has become an important part of modern life, industrial development and cutting-edge science. Optical thin films can be divided into anti-reflection coatings, high-reflection coatings, optical filters, spectroscopic coatings, etc. from the function, and can be divided into uniform dielectric films and non-uniform dielectric films from the structure. However, conventional optical thin film materials have their own definite refractive index, which cannot be flexibly adjusted. Facing today's increasingly complex application environment, optical films with a single refractive index can no longer meet the application requirements, such as the ideal anti-reflection on the surfa...

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Problems solved by technology

However, conventional optical thin film materials have a certain refractive index, which cannot be flexibly adjusted.

Facing today's increasingly complex application environment, optical films with a single refractive index can no longer meet the application requirements, such as the ideal anti-reflection on the surface of the substrate, you only need to find a material whose refractive index is equal to the product of the refractive index of the substrate under the root sign and the refractive index of the incident medium That’s enough, but the limited types of materials cannot well meet the needs of all application scenarios, and then it is necessary to use a multilayer film structure composed of alternate deposition of high and low refractive index materials, but the multilayer film structure is complex and difficult to design

The sol-gel method and the oblique deposition method are two conventional methods for preparing thin films with tunable refractive index. The principle is to reduce the refractive index of a single-layer film by preparing a loose porous film, but the two methods have a wide range of refractive index tuning. Limited, and poor controllability of refractive index

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