Experimental Studies On The Laser Performance Of LD Pumped Slab Geometry Tm:YLF Crystal

2μm laser was widely applied in the field of medicine, optoelectromic countermeasure, scientific reaserch and so on, due to its character of high damage threshold of the human eyes and strong atmosphere penetration. Tm:YLF crystal owns relatively more longer upper level lifetime, and it’s always the natural birefringent crystal which can obtain linear polorized laser. Besides, its emitting wavelength of1.91μm is located in the absorbing peak of Ho:YAG crystal.Therefore, Tm:YLF laser can be used excellent pump-source of Ho:YAG laser. The purpose of this thesis was to obtain the high power, high beam quality laser output with slab geometry Tm:YLF crystal pumping by LD.Firstly, we introduced the physical properties and spectral characters of Tm:YLF crystal.According to the Tm3+energy level transition theory, the theoretical model of the Tm ion doped quasi three-level rate equation was set up, and numerical simulated how the energy transfer-upconversion loss, the concentration and length of laser medium, the output coupler transmission and pump spot affected the output performance of the laser. Based on the heat conduction equation, the dual-end-pumped heat distribution model of slab crystal was built. The temperature ditribution in the crystal and stress ditribution were theoretial caculated. Simulate the temperature, strain and the stress distribution in crystal with MATLAB.Based on the above caculation, we carried out the experiment of dual-end-pumped slab geometry Tm:YLF laser. The pump source is the fiber-coupled output semiconductor laser with central wavelength of792nm，and adopted the plane concave cavity structure. In order to control the output wavelength, we chose the Volume Bragg Grating (VBG) as the totally reflecting mirror, meanwhile, a F-P etalon was inserted in the cavity. We also particularly studied the crystal’s output performance with different concentration and length, analyzed how the crystal parameters, the output mirror curvature and transmittance and the size of pump spot affected the output power. Also, we reaserched the how the crystal cutting axial,the diameter of fiber and the output mirror curvature affected the laser beam quality. Finally, we obtained1908nm laser output of82.3W under the pump spot radius0.84mm with the crystal dimention of1.7×6×35mm3and Tm-doping concentration2at.%, the output mirror curvature and transmittance repectively were40%and-200mm. The slope efficiency and optical-to-optical conversion efficiency were42.4%and36.9%respectively, the maximum incident pump power was223W. The beam quality factor of x and y direction were2.5and4.1with90/10knife-edge method under the the output power of69.5W.