高功率CO2激光器CVD金刚石窗口制备研究

本文研究制备了可应用于高功率CO₂激光器的CVD金刚石窗口。首先使用环形天线-椭球谐振腔式MPCVD装置沉积制备直径2英寸(1英寸=2.54 cm)金刚石自支撑膜,然后将膜片双面抛光,激光切割成矩形基片,再采用蒸镀法在基片表面制备中心波长在10.6 μm的增透膜,最终制备得到金刚石光学窗口。采用傅里叶红外透射谱、热导仪、爆破试验台测试了金刚石基片镀膜前后的红外透过率、热导率和爆破强度。利用自行搭建的光学平台,测试了CVD金刚石基片增透膜能承受的激光功率密度。结果显示CVD金刚石基片在10.6 μm处的透过率为70.9%,利用光谱计算的吸收系数为0.06 cm^-1,热导率＞19.5 W/(cm·K),爆破强度＞5.62 MPa,镀膜后的透过率为99.2%,增透膜可承受的激光功率密度＞995 W/mm²。

Preparation of CVD Diamond Window for High Power CO2 Laser

CVD diamond window which can be used in high power CO₂ laser was prepared. Firstly, a 2 inch diameter diamond self-supporting film was deposited by a circumferential antenna ellipsoidal cavity type MPCVD reactor. Then both sides of the film were polished, and the film was cut into rectangular samples by laser. An antireflective film with the central wavelength of 10.6 μm was prepared on the surface of the sample by vacuum evaporation. Finally, the diamond optical window was prepared. In this study, the infrared transmittance before and after coating, thermal conductivity and burst strength of diamond substrate were respectively measured by Fourier transform infrared spectroscopy, thermal conductivity meter and pressure blasting test stand. Using a self-built optical platform, the laser power density that the CVD diamond substrate antireflection coating can withstand was tested. The results show that the transmittance of CVD diamond substrate at 10.6 μm is 70.9%, the absorption coefficient calculated by spectrum is 0.06 cm^-1, the thermal conductivity is more than 19.5 W/(cm·K), the burst strength is more than 5.62 MPa, the transmittance with coating is 99.2%, and the laser power density that the AR coating can withstand>995 W/mm².