Measurement of weak absorption of thin film coatings irradiated by 10.6μm laser

The absorption of optical thin film coatings is one of the main factors that limit the development of high power lasers. It is necessary to measure the absorption of the optical thin film coatings precisely, fast and in real-time. The experimental setup for measuring the weak absorption of the optical thin films has been built using the surface thermal lensing technique. The weak absorption of different optical thin films, including the single-layer ZnS and YbF3 dielectric thin films with different thickness, as well as the different multilayer thin films (YbF3/ ZnS) deposited on Ge substrate, irradiated by 10.6μm CO2 laser has been measured. The experimental results show that the lowest absorption measured by the experimental system is 2.87×10－4 and the sensitivity of the experim