The Theoretical Analysis On The Thermal Effects In The Slab Laser Crystal

The geometry of Diode Pump Solid State Laser material were usually rodsor slabs. For the laser rods operated in the heat load conditions, the direction oftemperature gradient and light propagation were vertical, the laser rods would havea severe thermal lens effect and thermal distortion effect which made the light beamquality reduction and limited further increase of laser power. The temperaturegradient generally occurs in the direction of slab thickness within the slab lasercrystal, light propagation take the form of a definite zig-zag pattern when the totalinternal reffection was occurred between the two pumping surfaces, which made thepropagation direction of the light was paralleled to the direction of the temperaturegradient, and could avoided the thermal lens effect and thermal distortion, andsubstantially increased the laser output power besides. Therefore, the slab laser isbecoming the mainstream development direction of the high power diode pumpedsolid. Although slab laser can control heat and stress through its structure and thedepolarization and thermal focus can be effectively eliminate based on Zigzag path,thermal effects always restricted the slab laser developing to high power output andthe light beam quality. Accordingly research on the thermal effects have momentoussignificance to slab laser.The main content of the research in this dissertation is composed of three partsas follows,1. In the part of introduction, the structure of slab laser by diode array, thetemperature Control System for laser crystal, thermal effects in the slab laser andthe current research situation both at home and abroad are mentioned. Then themain content and purpose of this dissertation is given.2. The heat conduction equation of end pumped, edge pumped and facepumped slab laser by diode laser arrays was built, thereinto the edge pumped andface pumped were double-side pumping. Through solving the heat conduction equa-tion, the analytic expression of temperature field was obtained. Based on the above mentions, the thermal deformation distribution and the thermal focal length causedby non-uniform temperature gradient within the crystal were analyzed.3. The numerical simulation of one-dimensional temperature field, two-dimens-ional temperature field, thermal deformation and thermal focal length of five kindof crystal(Nd:YVO4,Nd:YAG,Nd:LuVO4 and Nd:GdVO4)were carried out withuse of mathematica software. Furthermore the simulation results were analyzed indetail.The heat conduction equation of slab laser and the analytic expression of tem-perature field obtained from this dissertation will supply theory for design and opti-mization of thermal effects. The numerical simulation of temperature field, thermaldeformation and thermal focal length of four kind of crystal can be a reasonablechoice to support the laser working medium.