Research on SiO2film laser damage threshold

Abstract

ABSTRACT The high energy laser put forward higher requirements about resistance laser damage ability of thin film on surface of optical component, this makes coating film not only consider the optical parameters of thin films, but also consider the film’s laser damage threshold to get the optical system work normally. mainly analyzing factors about effecting the SiO 2 thin film’s laser damage threshold and researching respectively the SiO 2 thin film’s optical parameters (such as extinction coefficient, thickness, refractive index and so on) an d light sources parameters of testing system (such as laser times of irradiation, pulse width and so on) impact on thin film laser damage threshold. Research shows that thin film optical parameters have little influence on laser damage threshold, testing laser parameters have great influence on laser damage threshold. Keywords : Laser damage threshold, lase r parameters, film parameters, irradiation time, PVAD, UBMS 1. INTRODUCTION With the progress of science and technology, the optical instruments are required in excellent performance. In the past, we often used ordinary optical systems, and now a laser optical system. Accordingly, natural light, as a radiation source, also became laser. When laser beams pass through optical system, it may damage optical thin film on the surface of the optical element. Therefore, problem of damage about optical thin film laser has been limited development of high energy laser, high power laser as a bottleneck. At the same time, the damage is a decisive factor that have an influence on life span of optical system[1-2].In addition, thin film element is widely used in missile, satellite and other space vehicle navigation, positioning, remote sensing and energy system. Thin film element damage can lead to blindness and even out of control of spacecraft. Regardless of f ilm on the optical element surface in lase r system, or film on the optical element surface of system attacked by the laser, we must consider the film may lost function or be damaged under some laser. Thin film the maximum capacity resistance damage under the laser irradiation is called laser damage threshold. To make the optical system to work normally, we must put forward so me requirements about the thin film resistance laser damage capacity. The thin film resistance laser damage capacity is measured w ith the laser damage threshold. Many factors influence the laser damage threshold, such as thin film thickness, refractive index, extinction coefficient and laser pulse irradiation times, pulse width and so on. Therefore, in order to improve the film laser damage threshold and measure accurately damage threshold, we must analyze relationship between these factors and damage threshold, and these factors how to influence damage threshold. so that thin film with high damage threshold can be made.