Optimization Of The Beam Quality Of LD Dual-End-Pumped Slab Laser With Folded-Three-Pass Resonator

Diode Pump Solid State Laser(DPSSL)occupies an indispensable position in the field of laser family due to its compact structure and high electro-optical efficiency.In this thesis,the development of DPSSL in China and aboard is analyzed and compared on the basis of the current research status of DPSSL.Several commonly used lasers are compared horizontally and the importance of DPSSL in high pulse field is explained.In order to deepen the application of DPSSL in the field of high pulse,slab crystal is used as gain medium,and the resonator is designed under the condition of stabilization to reduce the differences between the two directions,which contributes a lot to facilitate Q-switching and frequency doubling.For the purpose of compressing the mechanical size of the system,the concept of folded resonator is proposed to improve the gain performance of crystal and make it more widely used in the actual fields.In this thesis,starting from the three elements of laser:pump source,gain material and resonator,the principle analysis,device selection and scheme design of the system are carried out respectively.The laser beam shaping system is simulated and designed by Zemax.LD end-pumped folded-three-pass resonator,and a one-pass flat-concave resonator is set for performance comparison.The main research contents and results are as follows:(1)To optimize the beam quality of the system,combining with the equivalent cavity model of thermal effect,the slab crystal is equivalent to a thin lens.Using the simulation of MATLAB,the folded-three-pass resonator is optimized.With the idea of control variables,the resonator is optimized from the aspects of system stability,basic mode size and so on,and the optimized cavity scheme is obtained.(2)The folded-three-pass resonator and one-pass flat-concave resonator is measured by experiment.The output spot is measured by CCD.The beam quality M~2 factors in the direction of?and?are calculated respectively.Under the input power of 110A and 89.2W,the beam quality factors M~2 of one-pass resonator in the direction of?and?are 143.32 and1.99 respectively,and the beam quality factors M~2 of three-pass resonator in the direction of?and?are 2.76 and 1.54 respectively.(3)The performance of the folded-three-pass resonator is more outstanding than that of the previous generation.The design optimizes the cavity structure of the system,although the output power of the folding cavity decreases slightly,the beam quality in both directions has been significantly improved.At the same time,the thermal focal length of slab crystal is deduced from the experimental results,which reduces the system variables and lays a foundation for achieving better resonator mode in the future.