Optical thin film is a kind of functional thin film that uses the action of thin film on the light.  As an important optical element, it is widely used in modern optics, optoelectronics, optical engineering, and other related scientific and technological fields.  

The application of optical film is everywhere, from glasses coating to mobile phone, computer, TV LCD to LED lighting and so on, it is full of all aspects of our life, and make our life more colorful.  Let’s take a look at the application of the optical thin film.  

Application of optical thin film  

(1) optical film is used in optical instruments  

The lenses of many optical instruments are coated with optical films.  The lens of the telescope is not coated with optical film, so when the light hits the lens, some wavelengths of light will be reflected interference phase length, so that the intensity of reflected light is enhanced, transmission light is weakened, and other light will produce complementary colors, will affect the imaging of the telescope.  

The optical film can change the transmittance of light, so that the reflected light transmission is too large to enhance, and improve transmittance, at this time the anti-reflection film is used.  By controlling the thickness of the film, you can control which wavelengths of light are transmitted more or reflected more.  Coating the lens can not only improve the imaging quality of the telescope but also enhance the applicability of the telescope to various environments, such as snow, too strong reflected light will make the telescope imaging color dim distortion, serious chromatic aberration, coating the telescope with the red film will be a good solution to these problems.  

(2) optical film is used in lighting equipment  

The optical film is widely used in lighting equipment, such as incandescent lamps, low-pressure sodium lamps, etc., which can make lighting equipment more energy-saving.  Most of them are plated on the surface of the lamp with a layer of enhanced reflection film, which reflects infrared light very strongly. When the light shines on it, the interference phase is long, and the reflected light is enhanced to weaken the transmitted light so that the transmission of visible light is enhanced.  This can not only save energy but also change the energy distribution of the spectrum, so that the energy is mainly distributed in the visible light, little distributed in the infrared light, and even can make the energy in the infrared light to zero.  

(3) Application of optical film in agricultural production facilities  

We all know that light plays an important role in agricultural production. With the development of science and technology, a lot of agricultural cultivation is not so dependent on weather and season as in the past. Many fruits and vegetables are grown in greenhouses.  To make better use of light, a kind of sunshade energy-saving curtain film was invented, which is the use of optical film technology.  To save energy.  Now we have developed a new type of shading energy-saving curtain film, aluminum plating film on polymer material, energy-saving performance and regulating temperature effect is better, has reached the international advanced level.  

(4) Used in optical fiber communication  

Like an electronic circuit system, an optical fiber system needs many passive devices to connect, divide, combine, exchange, isolate and control or change the transmission characteristics of the optical signal.  The optical envelope plays a very important role in some of these instruments. 

In the lens beam extender connector, the lens surface needs to be coated with anti-reflection film to eliminate the effect of Fresnel reflection.  In a fiber directional coupling, part of the reflective dielectric film is plated on the combination of two lenses.  This kind of directional coupler composed of low light level elements is compact, simple, low insertion loss, and insensitive to power distribution of membrane, so it has been widely used.  Part of the dielectric reflection film can also be plated on a right-angle prism slanting to form a T-shaped coupling.  

Another optical wavelength division multiplexer (WDM), belongs to wavelength-selective coupling and is used to synthesize optical signals of different wavelengths or high wavelength optical signals of passive devices.  WDM can be designed and manufactured by various methods, among which the main characteristics of interference filter TYPE WDM devices are flat channel bandwidth, low insertion loss, small structure size, and stable performance.  

It is the use of multi-layer dielectric film as a filter, the specific structure has two types: one for interference filter, the other for absorption filter.  Both can be composed of dielectric jackets.  WDM film system generally uses 1/4 wavelength thickness, only using irregular thickness on both sides.  The monitoring method of the 1/4 wavelength thickness ventral system is simplified, and the extremum method can automatically compensate for the monitoring error of the base membrane.  The membrane system is in the form of multiple F-P degrees, and the coating material is titanium dioxide, which is commonly used.  

Silver-doped fiber amplifier (EDFA) is a practical active device in an optical communication system.  An optical coating filter is a commonly used method to improve the gain flattening of EDFA. In addition, a narrow band filter can be placed in front of the detector after EDFA to reduce the influence of noise.  

2. Conclusion  

Present optical and optoelectronic industry gets rapid development, in the device’s promotion and construction of the industry has made considerable progress, the preparation technology, the film system design, process control, features, test, and application development have carried out fruitful work, has a wide range of research results, and formed a certain scale of the industry.  Optical thin-film technology is the key technology required by laser technology, infrared technology, and aerospace technology, without the development of thin-film technology and optical thin film, there will be no modern technology and cutting-edge technology development.