Introduction of optical thin film absorption loss

Optical thin film has become an indispensable part of modern optical system, and its performance directly affects the performance of optical system. Absorption loss is an important parameter to measure the performance of optical thin films, especially in high-power laser systems, it has become the bottleneck of further improving the transmission power of optical systems. The absorption loss can not only cause the thermal distortion of optical thin film components, but also reduce the laser beam quality. It can also reduce the film's ability to resist laser damage and limit the maximum output and transmission power of laser and laser system. Accurate measurement of film absorption loss, especially absolute measurement, is very important to optimize the film design and coating process to improve the performance of thin film components.

The main sources of absorption are extinction coefficient of thin film material, interface pollution of thin film and properties of substrate; absorption leads to film damage, and absorption loss is large, and s can be obtained by testing R and T, and low absorption loss: high sensitivity method is used to test.

There are two methods to measure the absorption loss: one is to measure the extinction coefficient and absorption coefficient of the film; the other is to directly measure the absorption rate of the film, such as calorimetry.