Abstract

Recently years, with the shortage of energy resource in the earth and the wide application prospects of laser inertial confinement fusion (ICF) system, many countries have set up powerful laser driver facilities[1,2]. In these laser facilities, the Pockels cells and frequency multiplication devices made by large-aperture KDP crystals are widely used[3]. With the increasing of laser power, various nonlinear optical effects in the KDP crystal will significantly present, among which, Transverse Stimulated Ramam Scattering (TSRS) is one limiting the 3ω laser pulse intensity significantly[4-7]. Laser processing 3D microstructures inside KDP crystals is an effective way to suppress the TSRS in high power lasers. In this paper, a simulation study on the transmission characteristics of focused laser inside KDP crystal was carried out to investigate the feasibility of laser processing 3-D microstructures and the effects of laser parameters on the micromachining accuracy, efficiency and quality. The simulated results are in good agreement with experiments and show that the effects of the peak power density, spot distortion and deviation of laser focus are the main factors on the micromachining accuracy and quality. The size and shape of the extraordinary ray focus will distort and its peak power density decreases rapidly with the increasing of the angle between incident laser and crystal optical axis. The stimulated results also indicate that the effect of the extraordinary ray will make the processing efficiency increase more than double while the angle is less than 15°, and can be neglected if the laser was in the low-energy or easily causes crystal cracked if the laser was in high-energy while the angle is greater than 30°, in this case, the extraordinary ray must be isolated.

© 2012 Optical Society of America