Experimental study on Nd:YLF twostage doublepass offaxis amplifying system tightlysidepumped by high power LD array

A 10mm caliber twostage doublepass offaxis amplifying system was described, and the 5mm×5mm caliber laser pulse was amplified. The coupling system of high power LD array tightside directlypumping Nd:YLF rod was used. The characters of amplifying system and each amplification in different pump currents and input energy were analyzed by theory and experiment. In experiment when 1.58mJ energy was injected into the soft 5mm×5mm diaphragm, 129.2mJ energy was output, and energy extract efficiency was 19.5%.