Research On The Laser Damage Properties Of Optical Thin Films Prepared By PECVD

Optical thin films have been used almost in all optical systems, because it is easily damaged in the high power laser systems, a lot of scholars are focus on the research on the laser damage properties. Adopting the plasma enhanced chemical vapor deposition (PECVD) method can prepare films at low temperature, and also can achieve gradient refractive thin films deposition easily. The investigation on the change rule of laser-induced damage of optical thin films prepared by PECVD is of important significances to improving optical thin films laser-induced damage thresholds.The damage properties of optical films prepared by PECVD were investigated in this paper. Different thicknesses monolayer SiOxFy, SiO2, SiOxNy, SiNx thin films were prepared on BK7 glass substrate by PECVD, electric field intensity distribution of above four optical thin film samples under different thickness was simulated by software. Laser-induced damage thresholds and damage morphology were analyzed respectively. The relation between LIDT and optical thin film thickness, refractive, preparing parameter, electric field intensity distribution were established,1064nm minus filter of which the wavelength span 350nm to 3000nm was designed and optimized, it was prepared by homogeneous membrane and hybrid inhomogeneous membrane, the relation between LIDT and membrane was analyzed, the fabrication error by PECVD was discussed, and also accomplished environmental experiments. The main results are as follows:1) The LIDT of low refractive index materials such as SiOxFy and SiO2 thin films has little change with the thickness increase, LIDT of middle refractive index materials SiOxNy and high refractive index materials SiNx thin films has significant decrease with the thickness increase.2) Electric field intensity distribution has an obvious influence on the LIDT of SiOxFy, SiOxNy, SiNx thin films. For the SiO2 thin films, electric field chang has an little influence on the LIDT.3) Within the selected preparation process parameters, the influence of deposition temperature on the LIDT of SiOxFy and SiOxNy films is the most notable, radio frequency and working pressure have little impact. The influence of radio frequency on the LIDT of SiNx is the most notable, deposition temperature and working pressure have little impact.4) 1064nm minus filter was designed, in the passband, the average transmittance T≥92%, at the wavelength of 1064nm, the reflectance R≥95%. Finally, actual measured spectrum is almost the same as designed spectrum. LIDT of homogeneous membrane and hybrid inhomogeneous membrane is 10.9J/cm2 and 12.8J/cm2 respectively. (wavelength is 1064nm, pulse width is 10ns).5) Minus filter exhibited good environmental compatibility and environmental stability.