Subsurface defects of fused silica optics and laser induced damage at 351 nm.

Many kinds of subsurface defects are always present together in the subsurface of fused silica optics. It is imperfect that only one kind of defects is isolated to investigate its impact on laser damage. Therefore it is necessary to investigate the impact of subsurface defects on laser induced damage of fused silica optics with a comprehensive vision. In this work, we choose the fused silica samples manufactured by different vendors to characterize subsurface defects and measure laser induced damage. Contamination defects, subsurface damage (SSD), optical-thermal absorption and hardness of fused silica surface are characterized with time-of-flight secondary ion mass spectrometry (TOF-SIMS), fluorescence microscopy, photo-thermal common-path interferometer and fully automatic micro-hardness tester respectively. Laser induced damage threshold and damage density are measured by 351 nm nanosecond pulse laser. The correlations existing between defects and laser induced damage are analyzed. The results show that Cerium element and SSD both have a good correlation with laser-induced damage thresholds and damage density. Research results evaluate process technology of fused silica optics in China at present. Furthermore, the results can provide technique support for improving laser induced damage performance of fused silica.

Coupling method for laser-diode-array end-pumped solid-state amplifiers.

A new coupling method is proposed for high-power laser-diode-array (LDA) end-pumped large-aperture amplifiers. In this method, stacks in the LDA are distributed on a spherical surface, and a hollow duct is placed after them. Both numerical simulations and experimental research have been done for this method. All results show that high coupling efficiency and uniform pumping field can be obtained simultaneously using this method.

One-dimensional model of a plasma-electrode optical switch driven by one-pulse process.

In this paper, we present a one-dimensional simplified model for the processes of gaseous discharge and charging on the surfaces of KDP crystal for one-pulse process in Plasma-Electrode Pockels Cell (PEPC). The PEPCs are used as large-aperture optical switch in laser drivers for inertial-confinement fusion. The plasma electrodes of the switch are produced by high discharge current, while a high voltage pulse is applied across a thin KDP crystal plate through the helium discharge plasma. The evolvements of discharge current, charging voltage on KDP crystal and the switch efficiency of PEPC are simulated. The model is very useful for the design of PEPC and prediction the behavior of the optical switch.