The effect of the applied electric field on laser-induced damage of dielectric thin films

Laser-induced damage threshold (LIDT) in optical materials plays an important role in laser-matter interaction. The anti-laser ability of dielectric films are very important for the application in optical windows. In this paper, HfO2 and SiO2 dielectric thin films with thicknesses of about 240 nm and with good infrared characteristics are deposited by the vacuum thermal evaporation technique. The laser with peak density of 11 J cm(-2) is used to irradiate the dielectric thin films. The laser damage morphologies under different laser radiation densities and with or without external electrical fields are studied. The results indicate that the electron density excited by laser has a directly relationship with the absorption coefficient; the increasing electric field reduces the laser energy density, and decreases the optical absorption in the center of laser irradiation region, hence the laser damage area decreases.