Study On Generation Of Single Longitudinal Mode Pulses Based On Twisted Cavity Configuration And Passive Q-Switch

Since the birth of the laser device,demands for various lasers have been increasing,such as national defense construction,industrial production,information and communication.Especially for the solid-state laser with high energy,high repetition rate,high stability and high beam quality,it has an irreplaceable role in the research of the laser spectroscopy,optical parametric oscillator,laser-induced plasma,laser radar,inertial confinement fusion and so forth.All these lasers require a stable and efficient seed source;that is,a single longitudinal mode laser module.This paper introduces the research progress of single longitudinal mode laser at home and abroad,given the overall development of single longitudinal mode laser analysis,and discusses the deficiency in application,put forward the main research contents of this paper.Secondly,Jones matrix is derived,and the twisted-mode structure is verified to solve the spatial hole burning effect.The distribution and modulation depth of the intracavity inversion population are studied as a whole.The tran smission rate of the optimized Q-switched crystal without considering the transmittance of the output mirror is obtained.According to the simulation of the Q-switched rate equation with diffraction loss,variation trends of the output parameters of the Q switch are in accordance with the theoretical research.According to the characteristics of intracavity oscillation spectrum,the feasibility of this laser device is verified.Then,through the process of designing the oscillator with different structure,each cavity has its own matching degree in twisted-mode cavity structure.By changing the Q-switched crystal transmittance,overlapping angle of two wave planes,cavity length and repetition frequency.the theory at home and abroad with good accordance.Finally,the resonant outputs single longitudinal mode with pulse energy 9.7m J,pulse width 10.07 ns and repetitive frequency tunable laser pulse at 1~5Hz.M2 factor at x and Y axis is 1.23 and 1.47 respectively,and single longitudinal mode probability is greater than 98%.By utilizing the folded single-cell SBS structure,the output beam of the resonator is successfully compressed to 500 ps,and the energy reflectivity is 22.2%.Combining two technologies,a single longitudinal mode laser with higher peak power can be provided for production and scientific experiments.