Second Harmonic Generation

Investigations are being conducted under the subject contract with the objective of producing high average powers at a wavelength of 0.532 microns, with a short pulse and high repetition frequency format. The program objectives are to be achieved by utilizing a high average power CW NdYAG laser combined with electro-optic Q-switching technique and mode-locked pulse injection as a source of 1.065 micron radiation to drive a nonlinear crystal. To date, it has been demonstrated that mode-locked pulse injection combined with Q-switching in a CW high power NdYAG laser can be made to function reproducibly, creating substantial increases in peak power while yielding substantial enhancement in second harmonic conversion efficiency. The general conclusion that the authors have reached is that in order to produce average powers at 0.53 microns of greater than 20 watts it will be necessary to take steps to alleviate the thermal limitations of the harmonic generating crystals. This can be accomplished through an improvement in the materials themselves and the use of mechanical techniques which either distribute the thermal loading over a larger crystal volume or improve markedly the rate of heat removal. A discussion of these techniques will be presented in the final report.