Acousto-optic Q-switching 522nm Pr:YLF Single Frequency Laser

Single longitudinal mode(SLM)laser has the advantages of long coherent length,high beam quality and narrow spectral linewidth.Therefore,this kind of laser can be widely used in precision ranging,laser holography,high-resolution spectrum and other fields.Visible light laser in the range of green light spectrum have potential applications in the fields of coherent communication,display technology and optical data storage because of their unique advantages.The realization method of visible laser is mainly produced by several rare earth ions directly or indirectly,among which the nonlinear frequency conversion of neodymium-doped laser is a common scheme at present.By contrast,the praseodymium-doped laser has the spectral characteristics of direct lasing in visible band.which avoids the problems of the high sensitivity of phase matching,space deviation,thermal lens effect of nonlinear crystal,and laser-induced damage.Therefore,this paper proposes to use the Q-switching pre-lase technology combined with the Fabry-Perot(F-P)etalon,combined with Pr:YLF gain medium to achieve 522 nm SLM pulse laser output.In theoretical research,by analyzing the change of intracavity loss in the mode competition stage of pre-lase,the step function model of intracavity loss is introduced,and the four-level rate equation of pre-laser Pr:YLF laser is first established.The mathematical relations of pulse energy,peak power and pulse width with pump power are obtained by solving it,and the simulation is carried out.On this basis,combined with the theory of small signal gain,the process of the spectral variation in each stage of pre-lase is described mathematically.The transcendental equations satisfied by the linewidth,cavity length and mirror reflectivity of the pre-lase Pr:YLF laser are obtained.The linewidth characteristics of pre-lase Pr:YLF laser under different cavity length and reflectivity are obtained by simulation.In the experimental research,the experiment of 522 nm continuous-wave(CW)Pr:YLF laser is first carried out.Under the condition of free operation,the output threshold of the laser is 2.116 W.CW laser with the maximum output power of 1.26 W was obtained at the highest absorbed power of 7.44 W.Meanwhile,the output laser is operated in multi-longitudinal mode,and the cavity length is 98 mm.With the combined technology of pre-lase and F-P etalon,the experiment of 522 nm Pr:YLF SLM laser was further carried out.At the repetition rate of 20 k Hz,the threshold of the laser is raised to 3.886 W.The SLM pulse laser output with 3.05 μJ single pulse energy is obtained as the absorbed power increased to 5.69 W.The linewidth of SLM is 22 MHz.