Crystal coating is an important process in laser crystal applications. According to the crystal characteristics of neodymium-doped yttrium vanadate (Nd:YVO4), its intrinsic parameters, and optical film design theory, Ta2O5 and SiO2 were selected separately as high and low refractive index materials. The optical properties and surface roughness of the films were characterized by OptiLayer and Zygo interferometers, and the effects of ion source bias on refractive index and surface roughness were investigated so that the optimal ion source parameters were determined. Optical monitoring and quartz crystal control were combined to accurately control the thickness of each film layer and to reduce the monitoring error of film thickness. The prepared crystal device was successfully applied to the 1176 nm laser output system.

Yellow lasers have attracted much attention due to their applications in biomedicine, astronomy and spectroscopy, and the resonant cavity is an important part of lasers. In this work, the resonant cavity film was studied and prepared using physical vapor deposition (PVD) technology to couple and match the optical properties of Dy,Tb:LuLiF4 crystal to generate yellow laser. In the process of film deposition, the substrate temperature has an important influence on the quality of the film. Therefore, we first investigated the effect of HfO2 film quality at different substrate temperatures. Furthermore, the multilayer film was designed to couple and match the optical properties of Dy,Tb:LuLiF4 crystal. According to the designed film system scheme, HfO2 and UV-SiO2 were used as high- and low-refractive index film materials for resonant cavity film preparation using the PVD technique, and the effect of process parameters on the film quality was investigated. A 450 nm pump laser was used to directly pump Dy3+ to excite and generate the yellow laser. In this process, the excited radiation jump occurs in the crystal, and the generated laser in the new band reaches a certain threshold after oscillation and gain in the resonant cavity, thus successfully outputting a 575 nm yellow laser.

Optical coherence tomography is a new promising chromatographic imaging technique with the advantages of noncontact and high resolution without damage, which is widely used in the field of biological tissue detection and imaging. As an important optical element in the system, the wide-angle depolarizing reflector plays a key role in the accurate acquisition of optical signals. Ta2O5 and SiO2 are selected as the coating materials for the technical parameter requirements of the reflector in the system. Based on the basic theory of optical thin film and combined with MATLAB and OptiLayer software, the design of 0~60° incident 1064 ± 40 nm depolarizing reflective film is realized by establishing the evaluation function of the film system. To optimize the oxygen-charging distribution scheme during film deposition, the weak absorption properties of the film materials are characterized by optical thermal co-circuit interferometry. According to the sensitivity distribution of the film layer, the optical control monitoring scheme with a thickness error of less than 1% is designed rationally. “Crystal control + optical control” is used to precisely control the thickness of each film layer and complete the preparation of resonant cavity film. The measurement results show that the average reflectance is more than 99.5%, and the deviation of P-light and S-light is less than 1% in the 1064 ± 40 nm wavelength band range from 0° to 60°, which meets the requirements of optical coherence tomography system.