All Solid State Laser Device And Its Heat Effect

In recent years, using its fixed characteristics of the output wavelength of highpower semiconductor laser, gradually replaced the traditional xenon and krypton lampto pump the laser crystal, become the most widely used, the fastest developing newlaser. It has stable output, high efficiency, long service life, compact structure, easy touse, has become the hot spot and trend of the research and development ofinternational. At present in the environmental monitoring, medical and health, has abroad application prospect to exploration of the universe and other high-tech fields.Now, with the development of laser technology and the increasingly mature,significantly improve the laser beam quality, increase the stability, output power isobtained more and more, and the pulse width has been reduced, the production cost ismore and more low. However, on the basis of increasing output power of the laserbeam quality improvement, and thermal effect produced by the pump laser becomethe obstacle for further development and perfect, restricting the output characteristicof the laser, therefore, the theoretical study of the thermal effect of laser crystal hasbecome a focus of all solid state laser. This article through to vanadate crystalNd:YVO₄, Nd:LuVO₄, Nd:GdYVO₄as the gain medium of laser crystals, respectively,theoretical calculation and experimental research, through the comparison of a morereasonable boundary conditions. The main contents are as follows:1. We introduce the semiconductor pump laser development history and researchstatus, theoretical analysis of its working principle, including laser crystal materialincentives, solid laser, optical pumping system, thermal effect of optical pumpingsolid laser resonator, etc..2. The first time we compare Nd:LuVO₄first studied the diode pumped VanadateCrystals, Nd:YVO₄, Nd:GdYVO₄crystal under different boundary conditions of thetemperature field, the thermal focal length changes resulting from errors, and withexperimental results. In the case of Nd:YVO₄, the air temperature is16℃, pumpingpower is15W, fully consider the side and the end surface convection, the temperature peak inside the crystal by not considering the side and the end surface convection was205.67℃to188.84℃, thermal effect, significantly decreased, while the thermalfocal length changes from19.85cm to25.85, and experiment is more close to.3Analysis of the principle of the thermal lens effect and cause harm, how toreduce the thermal effect of crystal. Through the analysis and summary of the theoryof heat conduction, the cylindrical crystals with square crystal temperature fielddistribution, calculation further derived crystal thermal lens focal length.4. Based on the cylindrical crystal Nd:YAG with square crystal Nd:YVO₄comparison, we draw, produce changes in the crystal boundary conditions,temperature distribution of crystal will be significantly different, inside the crystaltemperature will have a greater change, boundary temperature change slightly, thethermal focal length will be different. Theoretical analysis and experimental datacomparison shows that: both the square crystal isotropic or anisotropic cylindricalcrystal, in consideration of its boundary convection heat transfer, significantlyincrease the crystal center field temperature, the corresponding boundary temperatureis increased, but the variation is small, while the thermal focal length is also a smallincrease; and while considering the lateral convection and end surface of theconducting case, crystal center field of lower temperature, the thermal focal lengthincreased, and with the pumping power increases or decreases, the crystal temperaturefield center temperature is proportional to the change, but the temperature differencewill become larger with the increase of the power, the thermal focal length will alsochange, crystal thermal effect is stronger, and reduce the crystal radius or increase theconvective heat transfer coefficient, temperature and heat center focal lengthcorresponding decreases, thermal effect is significantly reduced.