Accurate temperature measurement of a spectral beam combination grating based on VO2 film.

In a spectral beam combination system, temperature increase of the multilayer dielectric grating (MDG) worsens the far-field beam quality of the output laser. To accurately monitor the surface temperature of the MDG, this study deposits VO2 phase-change film on the lowest layer of multilayer dielectric films in the MDG and tests the transmittance with a probe laser. Based on this measurement, the surface temperature of the MDG can be calculated. Additionally, the study analyzes the influence of VO2 film on the surface electric field and the -1 diffraction efficiency of the MDG and presents a specific example of using VO2 film to test high reflector temperature. The study concludes that VO2 film is a feasible method of measuring temperature and better than an infrared thermal imager.