Laser Crystal Thermal Effect And Passively Q Switched Laser Characteristics

Laser diode-pumped all-solid-state lasers, which have drown a lot attentions recentyears, have a wide applications in many fields such as materials processing, military,medical, space communications, light display，optical interconnection, informationprocessing and scientific research fields, laser telecommunication, light display et. albecause of their ’s compact structure, high efficiency, small heat effect, high stability, longlife-time, high beam quality, wide wavelength ranges and various running modes.Comparing with actively Q-switched and mode-locked lasers, passively Q-switched ,which do not need any exterior driving devices, are of simple structures. During recentyears, the theory and experiment research of the slow saturable absorber Cr⁴⁺: YAG withexcellent physical and chemistry properties tended to be mature in generatinghigh-frequency impulse in infrared laser. The yellow light is widely used in display,medical ,field work especially in geodetic surveying in fog .yellow light is obtained mostlythrough the intracavity sum frequency technology.the technique of intracvity sumfrequency which is based on the dual wavelength operation have many difficulties in filmdesigns and particle number competitions,so the efficiency ,beam quality and stability ofthe light are not very ideal.This paper mainly research on the theory of the passivelyQ-switched yellow lasers and the thermal effect of the laser crystal .1.The progress of all-sold-state laser is introduced;the introduction of fundamentalprinciple and the classification of Q-switched .The summary of the production of thethermal of laser crystal and the ways of how to reduce laser crystal ’s thermal effect isgiven.2.The characters of Cr⁴⁺:YAG crystal ,the absorption proprieties and the spectralcharacteristics is given .Introduction of the mechanism of passively Q-switched andmode-lock through the Cr⁴⁺: YAG crystal energy level structure.3.Regarding frequency doubling process as an intracavity loss which changes with the transformation of the fundamental photon number,combined with the thermal loss ofcrystal and the gauss distribution of photon number density in intracavity,a couple of rateEquations describing the passively Q-switched intracavity frequency doubling yellowlasers are given. the theoretical simulation accord with experimental values well throughusing MATLAB.4.The description of crystal thermal model with rectangular and cylindrical aregiven.an introduction of finite difference method which resolve the the differentialequation is displayed.The formula of end deformation, optical path difference, and thethermal focal length these which are caused by thermal effect are deduced.In the end Thefactor of inducing thermal effect and the ways of how to reduce the thermal effect aresummarized.