The main optical thin film devices include reflective film, antireflection film, polarizing film, interference filter and spectroscope. They have been widely applied in the national economy and national defense construction, and have gained increasing attention from scientists and technicians. For example, the use of an antireflective film can reduce the loss of the luminous flux of a complex optical lens to ten times, and the output power of the laser can be multiplied by a reflector with high reflection ratio, and the efficiency and stability of the silicon photocell can be improved by using the optical thin film.
The simplest optical thin film model is smooth, isotropic homogeneous dielectric thin layer. In this case, we can use optical interference theory to study the optical properties of optical thin films. When a beam of monochromatic plane waves is incident on an optical film, there are many reflections and refractions on its two surfaces. The direction of the reflected light and refraction light is given by the law of reflection and the law of refraction. The amplitude of the reflected light and the refraction light is determined by the Fresnel formula (see refraction and Reflection on the interface).
The characteristics of optical thin film are that the surface is smooth and the interface between the layers is geometrically segmented; the refractive index of the film can be leaped on the interface, but it is continuous in the membrane; it can be a transparent medium or an absorbing medium; it can be uniform and not uniform. The films actually used are much more complex than ideal ones. This is because when the film is prepared, the optical and physical properties of the film deviate from the bulk material, the surface and the interface are rough, resulting in diffuse scattering of the beam; the interpenetration between the films forms a diffusion interface, and the anisotropy of the film is formed because of the growth, structure and stress of the film; the film is complex. The time effect of miscellaneous.
◆ The application of optical thin film is everywhere, from the goggles to the cell phone, the computer, the LCD of TV and the LED lighting. It is full of all aspects of our life and makes our life more colorful.
◆ The definition of optical thin film is that the thin and uniform dielectric film on the surface of the optical device is attached to the light in the propagation path, through the reflection, penetration (folding) and polarization characteristics of the layer of the layered medium to achieve all the light that we want in one or more wave segments. All reflective or polarized light separation and other special forms of light.
◆ Optical thin films can be divided into "geometric optics and physical optics". Geometric optics is a geometric form of dielectric film formed on the surface of an optical device to change the path of light to adjust or redistribute the beam; physical optics is a unique optical material element in nature through nanoscale to the required optical device. The dielectric film formed on the surface of the material is enhanced by changing the characteristics of optical material elements through the dielectric layer to change the functions of light polarization, transmission and reflection.
◆ The preparation conditions of optical thin films are usually high and fine, and the preparation and wet preparation of optical thin films are prepared. Dry preparation (including vacuum coating: evaporation plating, magnetron sputtering, ion plating, etc.) is generally used in the preparation of physical optical thin films, wet preparation method (including coating method, casting method, thermoplastic method, etc.) It is used in the preparation of geometric optical thin films.
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