Design And Research Of LD Dual-end-pumped Slab Laser With Folded-three-pass Resonator

Since the first ruby laser born in 1960,solid-state lasers have always been hotspots and focuses.With the development of semiconductor materials and LD-pump technologies,the DPSSL(diode-pumped all-solid-state lasers)have developed rapidly recently.DPSSL have many obvious advantages such as high conversion efficiency,high stability,long lifespan,compact structure and so on.DPSSL have been widely used in industrial applications and scientific researches.Traditional solid-state lasers chose rod crystal as gain medium.There is non-uniform temperature distribution during the operation of laser,because of low cooling efficiency and non-uniform distribution of pump.Thermal effect will do harm to beam quality and limit high power output ability,so slab lasers are proposed to reduce thermal lens effect.This dissertation presents theoretical and experimental researches of LD end-pumped slab laser with folded-three-pass resonator,main researches are summarized as follows:(1)The advantages of DPSSL are introduced by comparing DPSSL with lamp-pumped lasers;several different pumping methods of LD-pumped slab lasers are reviewed;(2)A novel LD end-pumped slab laser with compact folded-three-pass resonator is presented innovatively;gain medium and pumping system are analyzed and folded-three-pass resonator is designed;(3)The causes of thermal effect in gain medium are expounded.And the theoretical thermal equilibrium model is set up,temperature distribution and thermal-stress distribution are calculated and analyzed;(4)The equivalent cavity model of thermal lens effect is set up.The relative positions of mirrors and crystal in resonator are optimized according to beam radius of fundamental mode and thermal stability range of resonator;(5)Comparative tests are carried on,the output powers and beam sizes of Fabry-Perot resonator laser and folded-three-pass resonator laser are measured.The M~2 factors and transmission curves of output light beam are calculated.21W output power is obtained in folded-three-pass resonator laser.Comparing folded-three-pass resonator laser with Fabry-Perot resonator laser,horizontal M~2 factor is improved from 152.7 in to 10.8obviously,and horizontal beam size is compressed from 10.8mm to 4.1mm.These results indicate that LD-end-pumped folded-three-pass resonator slab laser has better output ability.