Search

Based on polarization state conversion, a technique for coaxially coherent combination of laser beams is introduced. Laser beams can be coaxially coupled into one beam with high combination efficiency and perfect beam quality. A polarized laser beam combination system based on master oscillator power amplifier (MOPA) configuration is developed and the efficiencies of both unit combination and the whole system are investigated. In the experiment of combining four beams with single longitudinal mode, a combination efficiency of 85.3% is achieved. It can be further enhanced by improving the stability of experimental environment and the quality of optical and mechanical components.

Ta_2O_5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition. The effects of SiO_2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated. The results show that SiO_2 protective layers exert little influence on the electric field intensity (EFI) distribution, microstructure and microdefect density but increase the absorption slightly. Annealing is effective on decreasing the microdefect density and the absorption of the films. Both SiO_2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT. Moreover, the maximal LIDT of Ta_2O_5 films is achieved by the combination of SiO_2 protective layers and annealing.