The optical coating is composed of thin film layers, which will produce interference effect to change the transmission or reflection performance of the optical system. The performance of optical coating depends on the number of layers, the thickness of each layer and the refractive index between different layers. Common coating types in precision optics include antireflective film (AR), high reflection (mirror) film, spectroscope film and filter film (short wave pass, long wave pass, notch wave, etc.). Antireflective film is applicable to most refractive optical elements, which can increase the luminous flux and reduce unnecessary reflection. High reflection film can provide large reflection in a single wavelength or a certain wavelength range, and is mostly used for mirrors. The spectroscope film is used to divide the incident light into transmitted light and reflected light output. Filter coating is applicable to a large number of life science and medical applications, and can transmit, reflect, absorb or attenuate light at a specific wavelength. Hanzhong Borisun Optics can also provide various customized coatings to meet your application needs.
Optical coating is usually applicable to specific incident angle and specific polarized light, such as S polarization, P polarization or random polarization. If the angle of light entering the coating is different from the design angle of incidence, the performance will be significantly reduced. If the deviation between the angle of incidence and the design angle of incidence is very large, the coating function may be completely lost. Similarly, using polarized light that is different from the designed polarized light will produce incorrect results.
The optical coating is made of deposited dielectric and metal materials, such as tantalum pentoxide (Ta2O5) and/or aluminum oxide (Al2O3) in alternate film layers. In order to achieve large or small interference in applications, the coating usually has a quarter wavelength optical thickness (QWOT) or a half wavelength optical thickness (HWOT). These films are made of layers with high refractive index and low refractive index alternately, thus inducing interference effect.