Laser damage threshold of optical components is an important indicator to measure the ability of components to resist laser damage. A low-absorption film is plated on the surface of the reaction sintered SiC substrate produced by ion beam sputtering method, and the fundamental frequency reflection efficiency is over 99.8%. A set of 1060 nm continuous laser damage threshold testing system has been established. After loading the SiC-based film sample with a continuous wave laser with a power density of 30 kW/cm2 for 30 s, it was found that the surface temperature rise of the SiC-based film was less than 2 K. the changes of temperature field and thermal stress on the surface of the SiC mirror when the continuous laser loading power and loading time by finite element method. The results are basically consistent with the experimental data. The experimental results verify that the thermal stress and thermal melting effect caused by high-power continuous laser loading are the mechanisms for the damage of mirrors, which provides an idea for improving the laser damage threshold of optical components.
Ta2O5/SiO2 mixture films with different composition ratios deposited by ion-beam sputtering were investigated. The different refractive indexes with different composition ratios were measured by Spectroscopic Ellipsometry. The relations between residual stress and structural properties were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the high compressive stress observed in SiO2 films (n=1.65-2.0, Ref. λ=500nm) was reduced significantly by mixing a properly amount of Ta2O5 (σTa2O5=-234MPa<σSiO2=-510MPa). Through analyzing microstructure properties and optical properties of Ta2O5/SiO2 mixture films, we found that the residual compressive stress was only related with the intrinsic stress σintr and the extrinsic stress σext. A model of stress evolution has been proposed to illustrate the mechanism of stress reduction . The reduction of compressive stress was due to less lattice mismatch and more vacancies. Moreover, the scanning electron microscopy (SEM) result showed that the surface quality of SiO2 film was improved by mixing a relatively amount of Ta2O5 (n=1.85, Ref. λ=500nm).
Gd2O3 thin films were deposited by Ion-beam sputtering (IBS) under the oxygen flow of 0 sccm~30 sccm. The structure and optical properties of the Gd2O3 optical films were investigated by Lambdar950 spectrophotometer, laser calorimetry and atomic force microscopy (AFM). When oxygen flow was less than 10 sccm, with the increase of oxygen flow, the transmittance of the films increased, at the same time absorptance and the surface roughness of the films decreased. While the flow was more than 10 sccm, with the increase of the flow rate, the surface roughness of the films increased, but the transmittance and absorptance did not show any apparent change. The results show that both the structure and optical properties are closely related to the flow of oxygen. XPS measurements demonstrated that when the oxygen flow increase from 0 sccm to 10 sccm, the defect oxygen decreases. But when the oxygen flow increase from 10 sccm to 30 sccm, the defect oxygen increase. The XPS spectra show that when the oxygen flow was 10 sccm, the defect oxygen was the least. Thus when the oxygen flow was 10 sccm, the structure and optical properties of the Gd2O3 optical films were the best.
We present a model to describe the mechanism of laser induced electronic damage in optical coatings. Different from the classical laser damage models, the electron tunneling effect is taken into account in our model. The diffusion of free electron in the conduction band is enhanced if free electron tunnel effect happens in the optical coatings. Under some specific circumstance, the electron tunneling effect will make a great impact on the laser induced damage properties of the optical coatings. Under radiation of different duration and different power intensity lasers, the influence of free electron tunnel to the laser induced damage threshold is also different. Based on the calculation results, the tunnel effect can influence the laser induced damage properties of optical coating system at nanosecond and picosecond regime. In the femtosecond regime, the influence of the tunnel effect can be neglected.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.