Abstract
The non-linear optical coefficient of Lithium Niobate (LiNbO3) crystal is great, and can utilize the high voltage to transfer it to PPLN (Periodically Poled Lithium Niobate) crystal. QPM(quasi-phase matching) technique enlarges non-linear optical coefficient and expands the applications in many domains such as military, environmental monitor, medical treatments, quantity examining, long distance measurements and spectroscopy…etc. For producing high power infrared, one utilized two stages methods to fabricate 1mm thickness PPLN with period 29.6um. Not only one overcame the problems during high voltage poling (~22kV) and collected many valuable parameters, but proposed a high power infrared laser structure sufficiently used the advantages of this large cross section PPLN crystal. One had succeeded in fabricating 35mm-long, 5mm-width and 1mm thickness PPLN with the period is 29.6um. In OPG, at the 2 mJ pump pulse energy, it generated 829uJ and 395uJ pulse energy; 41.5% and 19.8% conversion efficiency at the signal and idler wavelengths, respectively. The total conversion efficiency of OPG process is about 61.2%. For getting best output coupler at signal wave, utilize whirling BK7 glass of its Fresnel reflection characteristic to simulate tunable output coupler reflection. One obtained two values, 50% and 75%. Finally, one has carried on a series of OPO experiments with different output coupler. All these efforts were for the sake of preparations for a high power infrared laser one proposed.