Analysis of defect induced light intensification due to second-order effect in high power laser systems

摘要

In this paper, a new mechanism of hot image formation introduced in frequency conversion process is introduced. Under the effect of second order nonlinear effect, defects can also cause downstream hot image, where the peak light intensity can reach several times of the average light intensity. The corresponding physical model was established, and the physical process and related laws of the upstream defect induced optical field enhancement under the second order nonlinear action were studied by theoretical analysis and numerical simulation. It is found that three wavelengths of laser will form corresponding hot images at different positions downstream of the nonlinear crystal. The effects of defect size and conversion efficiency on hot image strength are further studied. Finally it is found that the generation of hot image of triple frequency can be effectively inhibited by increasing the spacing between two crystals. This research can provide an important reference for beam quality control of final optical systems of high power laser deriver.