Theoretical Study Of The Q-switched Intracavity Frequency-doubled Raman Laser Considering The Multi-transverse-mode Of The Fundamental Laser

Raman yellow lasers with wavelengths ranging from 560nm to 600nm are widely used in information storage,medical,laser display,atmospheric testing,DNA sequencing and communications.Solid Raman yellow lasers have been widely studied because of their high efficiency,stability,and compact internal structure of laser resonators,making them a hot topic of research and exploration in solid lasers and nonlinear optics.Since the stimulated Raman scattering effect has no phase matching restriction,the output beam has many excellent characteristics such as high quality,high brightness,good coherence of laser,high efficiency,and the like.The laser rate equation is an effective tool for analyzing the characteristics of Q-switched pulsed lasers.The current cavity Raman laser rate equation is established using a plane wave approximation or a single transverse mode approximation,which is inconsistent with the actual operation of the fundamental frequency laser and cannot explain the effects of multiple transverse mode operation of the fundamental frequency laser on the frequency-doubled laser output.The theoretical model of the inner-cavity Raman laser rate equations considering the multi-transverse-mode oscillation of the fundamental frequency laser is more suitable to the actual situation than the plane wave approximation and the fundamental frequency single transverse mode approximation.The effect of mode oscillation on frequency-doubled laser output.The experiment uses Nd:GdVO₄ as a Raman crystal,KTP as a frequency-doubled crystal,and Cr⁴⁺:YAG as a saturable absorber.Using a compact and straight cavity structure under different pumping power,the pulse repetition rate is changed by the actively Q-switched method.The relationship between the output power of the frequency-doubled laser and the pulse repetition rate is obtained.When the pulse repetition rate is 15kHz,the output power of the yellow laser is 1.156W,and an efficient conversion efficiency of 12.1%is obtained,and the passively Q-switching mode is used differently.The initial transmission rate of the saturable absorber has obtained the influence of the initial transmittance of the saturable absorber on the frequency-doubled laser output.When the T₀ is 89%,the output power of the yellow laser is 320mW,and a 5%efficient conversion efficiency is obtained.