Study On The Influencing Factors Of Output Characteristics Of Passively Q-switched Yb:YAG Laser

Yb:YAG laser crystal has the characteristics of absorption bandwidth which can be completely cover spectral width laser diode pump sources are used to launch,simple energy level structure,low heat consumption,high efficiency,igh doping concentration and so on,Yb:YAG solid laser pumped by laser diode has become a hot research topic,and has become a major research direction of high efficiency and high power solid state lasers,it has been widely used in many fields of production and life,national defense etc.In this paper,the purpose is designing a compact Yb:YAG laser.At first,the research status of Yb:YAG laser pumped by the laser diode at home and abroad is analysed,and then the basic characteristics of Yb:YAG laser crystal,band structure,absorption spectra and emission spectra is discussed,Laser forming condition and output characteristics is studied based on the rate equation.In this paper,according to the rationale of q-switching technique and the condition to realize q-switching technique,the characteristics of active Q and passive Q is compared,the basic characteristics of saturable absorber Cr⁴⁺:YAG crystal and the necessary condition as saturated absorber of passive Q are analysed.The output characteristics of laser burst of passive Q is also studied by simulation calculation,from passive Q coupling rate equations of Cr⁴⁺:YAG.It is found that the pulse width decreases with the increase of pump power,and the peak power and repetition rate increase;With the increase of the transmittance of the output mirror,the peak power increases and the repetition frequency decreases;With the increase of the initial transmission rate of the passively modulated Q saturable absorber,the peak power decreases and the pulse width and repetition rate increases.The experimental prototype of laser is designed.From selection of experimental equipment,the relationship of the absorption coefficient and doping concentration of the Yb:YAG laser crystal,we carry on a systemic analysis,finally Yb:YAG laser in the optical experiment platform is built.From the experimental data,it is found that the laser output power increases with the decrease of the laser cavity when the concentration of the laser crystal,the operating temperature,and the transmittance of the output mirror is constant;when the length of the laser cavity,the operating temperature,and the transmittance of the output mirror is constant,the laser output power significantly increase when crystal doping is10at.%relative to it 5at.%;when the length of the laser cavity,the concentration of the laser crystal and the operating temperature is constant,the laser output power when transmittance of the output mirror is 7%is bigger than when transmittance of the output mirror is 4%and 10%;when the length of the laser cavity,the concentration of the laser crystal and the transmittance of the output mirror is constant,the output power of the laser becomes larger with the decrease of the operating temperature of the laser crystal.In addition,the Cr⁴⁺:YAG passive Q-switched Yb:YAG laser with pulse width of 2.45ns and repetition frequency of 1.5kHz is developed by experiment,and the output characteristic of laser burst when Cr⁴⁺:YAG crystal do saturable absorber of passive Q is also studied.