Research On Thermal Effect Of High Power LD Pumped Solid-State Laser

Compared with traditional solid-state lasers pumped by flash lamps, diode pumped solid-state laser (abbreviated to DPSSL) has lower thermal effect. But, to a certain extent, thermal effects still restrict the DPSSL from giving out a high power and high energy output as desired. In this dissertation, thermal effects of repeated-pulse solid-state laser and heat capacity laser, especially end-pumped and side-pumped repeated-pulse laser, have been analyzed by finite element method and IR camera. The main results obtained in the dissertation can be summarized as follows:Firstly, a finite element thermal model of repeated pulse LDA (Laser Diode Array) end-pumped laser crystal Nd:YLF is established. 3D and transient distributions of temperature and thermal stress in laser crystal were calculated. The results show that the maximal temperature and thermal stress increase with pump power linearly, and fracture due to thermal stress may occur when effective pump energy up to 10 kW/cm2; the thermal effect of crystal under Super-Gaussian transverse distribution is the weakest when pumped by same power.Secondly, in end-pumped repeated pulse laser, thermal effects rise definitely when the frequency increases. When the heat transfer coefficient increase, the maximal temperature will decrease, but the maximal thermal stress may not decrease, the crystal can't work safely only by the increase of heat transfer coefficient. Some of the conclusions have been verified by experiment.Thirdly, pump efficiency and thermal effect in ring-LDA pulse-side-pumped Nd:glass laser have been studied. When designing a pump structure of specified gain amplifier, we start with LDA ring radius, and the highest pump efficiency can be achieved. Based on the same gain coefficient, the smaller glass radius is, the lower pump power needed and the lower thermal effects are.Finally, although LDA pumped heat capacity laser has partially eliminate the thermal effect of high average power laser, thermal effect due to the non-uniform pump can not be neglected. By means of 3D heat transfer codes and experimental measurement, the temperature and thermal stress distribution have been researched.The conclusions in this dissertation can be used to optimize and operate the high power DPSSL.