Thermal Effect Of LD End-pumped Laser Crystal With Circular Cross–Section

High power diode pumping all-solid-state lasers have recently attracted muchmore interest for their unique merits, such as long lifetime, compact structure, highstability and optical–optical conversion efficiency，etc. It employs diode laser as thepump source instead of conventional Helium or Xenon flashlamp, leading to asignificant improvement of efficiency, reliability and beam quality, and thus called therevolution of the laser history. With the development of high power diode lasers, highpower DPSSL has become one of the main objectives of current research anddevelopment activities within the laser community. Research of DPSSL has mainlyconcentrated on scaling of output power, while remaining of a high spatial beam quality.The main problem hindering scaling of diode-pumped solid-state lasers is heatdeposition within the laser medium. Laser crystal is the core of diode-pumpedall-solid-state lasers, which decide the output characteristics of laser. In recent years, inendeavoring to obtain higher output powers from continuous-wave end-pumpedsolid-state lasers, one must consider thermal effects that will impact opticalperformance.The thermal effect of Nd:YVO4crystal rods induced by laser diode-pumped is alsoanalyzed theoretically in this paper, the more rational boundary conditions areestablished considering the distribution of laser beam in the crystal and the heatconvection between the side surface of the crystal and the coolant, as a result, the moreactual temperature field in the crystal is obtained, and simultaneously the influences ofcrystal radius and pimp power on thermal effect are calculated.The thermal effect of Nd:YAG crystal rods induced by laser diode-pumped is alsoanalyzed theoretically in this paper, the more rational boundary conditions areestablished considering the heat convection between the side surface of the crystal andthe coolant as well as the convective heat-transfer about the pumped surface, as a result,the more actual temperature field in the crystal is obtained, and simultaneously theinfluences of crystal radius and pimp power on thermal effect are calculated.The contents can be outlined as follows:1. Reviewed the history and progress of diode-pumped solid-state lasers; andanalysed the characters of the diode-end-pumped solid-state laser, such as incentive mode, the way of pumping, the laser medium structure, the solid laser crystal materialsof LD-pumped.2. The cause of engendering and the disadvantage of laser crystal as well as themethod of reducing thermal effects was presented. On the basis of thermal conductivity,the equation of square and round laser crystal was established. We explain the theoryof focal length.3. The thermal effect of Nd:YVO4crystal rods induced by laser diode-pumped isalso analyzed theoretically in this paper, the more rational boundary conditions areestablished considering the distribution of laser beam in the crystal and the heatconvection between the side surface of the crystal and the coolant, as a result, the moreactual temperature field in the crystal is obtained, and simultaneously the influences ofcrystal radius and pimp power on thermal effect are calculated. The results show that thetemperature in the center and on the side surface of the crystal increases when theconvective heat-transfer about the side surface is considered. As increasing the pumppower and crystal radius, the temperature of the crystal increases, considering theconvective heat-transfer about the side surface, the temperature different is wider.4. The thermal effect of Nd:YAG crystal rods induced by laser diode-pumped isalso analyzed theoretically in this paper, the more rational boundary conditions areestablished considering the heat convection between the side surface of the crystal andthe coolant as well as the convective heat-transfer about the pumped surface, as a result,the more actual temperature field in the crystal is obtained, and simultaneously theinfluences of crystal radius and pimp power on thermal effect are calculated. The resultsshow that the temperature in the center and on the side surface of the crystal increases,correspondingly the focal length of crystal increase a little bit when the convectiveheat-transfer about the side surface is considered. Considering the heat convectionbetween the side surface of the crystal and the coolant as well as the convectiveheat-transfer about the pumped surface, the temperature in the center and on the sidesurface of the crystal is lower and the focal length increases. But the temperature ishigher and the focal length increases and than that when only considering convectiveheat-transfer about the pumped surface; Increasing pump power ,the temperature in thecenter and the focal length increases when the temperature different is wider at differentboundary condition; When decreasing the crystal radius, the temperature in the centerand decreases. Enhancing the air heat transfer coefficient, the thermal of crystal centerwas reduced sharply, the thermal focal length was increased, and the thermal effect was weakened.