What is optical coating?

Optical coating refers to the process of plating a layer (or multilayer) of metal (or medium) film on the surface of optical parts.  The purpose of coating the surface of optical parts is to reduce or increase the reflection, beam splitting, color separation, filtering, polarization and other requirements of light. Commonly used coating method has vacuum coating (a physical coating) and chemical coating.  

Coating is a physical or chemical method to coat the surface of a material with a layer of transparent electrolyte film, or a layer of metal film, the purpose is to change the reflection and transmission characteristics of the material surface.  

Most metals have a reflectivity of 78% to 98% in the visible and infrared bands, but no higher than 98%.  Both for CO2 laser, the use of copper, molybdenum, silicon and germanium, etc to make reflectors, germanium and gallium arsenide, zinc selenide and transmission optical element as the output window material, or for YAG laser adopt ordinary optical glass as a mirror, output mirror and transmission optical element material, can't meet the requirements of more than 99% of the total reflection mirror.  The transmittance of output mirror is different in different applications, so optical coating method must be adopted.  

Optical coating's materials - zinc sulfide, magnesium fluoride, titanium dioxide  and zirconia

For the INFRARED band of CO2 laser lamp, the commonly used coating materials are yttrium fluoride, praseodymium fluoride, germanium, etc. For THE near infrared band or visible band of YAG laser lamp, the commonly used coating materials are zinc sulfide, magnesium fluoride, titanium dioxide, zirconia and so on.  In addition to high reflection film, anti-reflection film, can also be plated on a wavelength of increased reflection, on another wavelength of increased transmission of special films, such as laser frequency doubling technology in the spectroscopic film.