The Thermal Effect Of LD End-pumped Laser Crystal

Diode-pumped all-solid-state lasers(DPSSL) has lots of advantages,such as compact structure, high stability and optical-optical conversion efficiency. It is widely used in national defence, photoelectron industry, communication, medical treatment and sanitation. With the development of high power diode lasers, high power DPSSL has become one of the main objectives of current research and development activities within the laser community. Research of DPSSL has mainly concentrated 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 heat deposition within the laser medium.Laser crystal is the core of diode-pumped all-solid-state lasers, which decide the output characteristics of laser. In recent years, in endeavoring to obtain higher output powers from continuous-wave end-pumped solid-state lasers, one must consider thermal effects that will impact optical performance.The thermal effect of rectangular-face Nd:YVO4 has been calculated. The focal length of the laser crystal is obtained by calculating the temperature distribution in the crystal. Simultaneously the influences of crystal radius and side surface area on thermal effect are calculated.The thermal effect of Nd:YAG crystal rods induced by laser diode-pumped is also analyzed theoretically in this paper, the more rational boundary conditions are established considering the distribution of laser beam in the crystal and the heat convection between the side surface of the crystal and the coolant, as a result, the more actual temperature field in the crystal is obtained, and simultaneously the influences of crystal radius and side surface area on thermal effect are calculated.The history and progress of diode-pumped solid-state blue light lasers was introduced in this paper. Using plane- concave cavity, the blue light was obtained by Nd:YAG-LBO.The contents can be outlined as follows:1. Reviewed the history and progress of diode-pumped solid-state lasers; and analysed the characters of the diode-end-pumped solid-state laser; The history and progress of diode-pumped solid-state blue light lasers was also introduced.2. The cause of engendering and the harmful effect of laser crystal was presented. On the basis of the thermal effect theory of laser crystal, the thermal conduct model of laser crystal was established. Using Possion equation, the temperature distribution in laser crystal was obstained, and the OPD were caculated. Based on the former calculation, we obtained the focal length of laser crystal.3. The thermal effect of rectangular-face Nd:YVO4 has been calculated. The OPD and the focal length of the laser crystal is obtained by calculating the temperature distribution in the crystal. Simultaneously the influences of crystal radius and side surface area on thermal effect are calculated. The thermal effect of Nd:YAG crystal rods induced by laser diode-pumped is analyzed theoretically in this paper, the more rational boundary conditions are established considering the distribution of laser beam in the crystal and the heat convection between the side surface of the crystal and the coolant, as a result, the more actual temperature field in the crystal is obtained, and simultaneously the influences of crystal radius and side surface area on thermal effect are calculated. The results show that the temperature in the center and on the side surface of the crystal increases when the convective heat-transfer about the side surface is considered, correspondingly the focal length of crystal increase a little bit. As decreasing the crystal radius, the differences in temperature between the center and the side surface of the crystal decrease, the focal length of crystal increases and the thermal effect of the crystal reduces; As increasing the side surface area, the temperature of the crystal decreases, but change rate of temperature nearby the crystal center increases for the feature of end-pumped, as a result, the focal length of crystal decreases and the thermal effect aggravates.4. The characteristic of Nd:YAG. and the characteristics for frequency-doubled of LBO was introduced . We adopted the simple plano-concave cavity, when the incident power was 7.33W ,produced 220mW output power at the wavelength of 473nm with the nonlinear crystal LBO.