Optical Film In The Process Of Laser Heat Absorption And Thermal Stress

Optical components of the high power laser system must complete certain functions during process of the ICF (inertial confinement fusion) drived by high power laser. This requires depositing different materials and different layers of optical coatings on the substrate. However, it is showed by the results of the experiments that a particular weak point is the components with optical coatings, which have become a key problem hampering the further increase in the output of laser equipment. And its damage mechanisms become the study issue of the field.A set of laser induced damage threshold (LIDT) testing system based on ISO standard 11254-1.2 was established, so was a set of surface thermal lens (STL) testing system. The former is automatic and can help us to improve precision and efficiency of LIDT test, and the latter can provide the weak absorption of the thin films, also embody the thermal distortion and observe the dynamic process of the damage. And combined with the microscopic observation, this paper studies high-power laser-induced damage of several types of single-layer and multilayer thin films on K9 substrates:1). Two types of single-layer SiO₂ thin films, which were respectively deposited by ion-beam sputtering deposit (IBSD) technique and sol-gel technique. The measurment results showed that the weak absorption of IBSD SiO₂ thin film is far higher than that of Sol-Gel SiO₂ thin film,and brings forward that the dense IBSD physical thin film has rapid conductive thermal shock effect with high absorption under laser irradiation, then is more obviously affected by the substrate material, the damage threshold is 21.88 J/cm² under condition of 1.06μm wavelenght and 3ns pulse duration. However, the chemical thin film with low absorption has opposite condition and the loose interspaces in the film can delay the thermal conduction,then is affected little by the substrate material, and the damage threshold is 41.61 J/cm² under corresponding condition.2). Another three types of thin films on K9 substrates deposited by ion-beam sputtering deposit(IBSD) technique, which are respectively single-layer films,multilayer anti-reflective films and reflective films.With the same experimental means above, we also discussed the threshold difference among the IBSD thin films in detail, and found...