The main optical thin film devices include reflective film, antireflective film, polarizing film, interference filter and spectrometer.

They have been widely used in national economy and national defense construction, and have been paid more and more attention by scientists and technicians. For example, using antireflection film can reduce the luminous flux loss of complex optical lens by ten times, using high reflectance mirror can double the output power of laser, and using optical film can improve the efficiency and stability of silicon photocell.

1、 Structure

The simplest optical thin film model is a homogeneous thin layer with smooth and isotropic surface. In this case, we can use the interference theory to study the optical properties of optical films. When a monochromatic plane wave is incident on an optical film, multiple reflections and refractions occur on its two surfaces. The directions of the reflected and refracted light are given by the law of reflection and refraction, and the amplitudes of the reflected and refracted light are determined by Fresnel formula.

2、 Characteristics

The characteristics of optical thin film are: smooth surface, geometric segmentation of the interface between the films, the refractive index of the film can jump on the interface, but it is continuous in the film, which can be transparent medium or optical thin film.

Absorption medium: it can be normal uniform or non-uniform. The practical application of the film is much more complex than the ideal film. This is because, during the preparation, the optical and physical properties of the film deviate from the bulk material, and its surface and interface are rough, which leads to the diffuse scattering of the light beam, and the mutual penetration between the film layers forms the diffusion interface The anisotropy of the film is caused by the structure, stress and so on. The film has complex time effect.