Large-diameter Fused Silica Surface Of The Component Laser Damage Characteristics Of Study

Laser-induced damage of the large-aperture fused silica optics, especially the surface damage, would decrease the optics' lifetime and has been the main limiter of improving the load capacity of the Inertial Confinement Fusion (ICF) laser driver. This thesis mainly focuses on the surface damage of the large-aperture fused silica and obtains results by theoritical and experimental research. The main content of the thesis can be summarized as follows:The issue of the load capacity in ICF laser is brought out and the historical review of NIF's effort of improving the load capacity is presented. The mechanisms of laser-induced damage at fused silica surface are summarized.It is believed the damage is mainly casued by the inclusions introduced in grinding and polishing process.The probability model of the surface damage of fused silica is set up. Based on the absorbing mechanism of the inclusions and the inclusions' radius distribution, the damage threshold distribution of the inclusions is obtained. Combined with the random ditribution of the inclusions on the surface, the form of the probability curve P(F,S) of damage is deduced. With this curve, the damage threshold and the initial damage density measuerd under different conditions could be predicted.A confirmative experiment is done. A prediction from the threshold data obtained by a small-aperture laser accords the threshold in TIL experiment. Thus the probability model is validated.The analytical expression of the initial damage area is deduced based on the relationship between the laser energy and the area of the damage crater.The static probability model is further developed. The relationship between the changes of damage density, obscuration and the fluence, radiation area and pulse number is deduced.Thus a method to predict the damage threhold, damage density and obscuration under functional conditions from the data obtained from off-line damage test is set up. By this method, the damage performance and life-time of optics could be evaluated off-line. It could provide guidance to run the optics more efficient.Besides, the effect of multiple wavelengths to damage is briefly discussed.For the non-absorbing inclusions, the scattering and the nonlinear propagation of the light field is simulated by finite difference time domain and split Fourier arithmetic separately. The simulation shows the voids and zirconia inclusions of radius comparable to the wavelength amplify the electromagnetic field amplitude by about 1.6 and 1.9 and after the nonlinear transportation the modulation increases and the beam splits. The results present that the bulk inclusions could cause damage at the rear surface and deterioration of the beam quality.The methods and results in this thesis would benefit improving the load capacity of high power solid-state laser in our country.