Study On The Laser Performance Of VB Group Crystal Based On Direct Pumping And Two-dimensional Selenide Materials

Diode laser-pumped solid-state lasers?DPSSL?are widely used in various scientific research fields due to their compactness,high energy conversion efficiency,and excellent output beam quality.With the continuous development of DPSSL,various crystal materials have been used as gain media.In recent years,two new single crystals Nd:GdNbO₄ and Nd:GdTaO₄ have been successfully developed.Given that Nd:GdVO₄ and other vanadates have excellent laser performance,and niobium?Nb?,tantalum?Ta?and vanadium?V?elements are in the same family of the periodic table of chemical elements,so the optical properties of these two crystals have attracted people's interest,and previous studies have initially demonstrated some of the superior properties of the two new crystals.Continued research on such gain media can expand the family of gain medium materials.Therefore,scholars expect to detect more comprehensive laser performance of Nd:GdNbO₄ and Nd:GdTaO₄ crystals.In the pumping method,direct pumping has been used more and more because it can improve the photon conversion efficiency and reduce the thermal effect of the crystal effectively.Since graphene was successfully separated in 2004,more and more two-dimensional materials have been developed and used widely.Recently,the two-dimensional materials of selenide represented by SnSe₂,PdSe₂ and ReS₂ have been proved to have ultra-fast recovery time,ultra-thin thickness and wide spectral range.Therefore,this work will discuss the Q-switched pulsed laser based on direct pumped Nd:GdNbO₄/Nd:GdTaO₄ and new types of selenide two-dimensional material.In this work,the basic characteristics and research progress in recent years of the two crystals were introduced briefly,and the advantages of direct pumping was summarized from the analysis of energy level structure in the selection of pumping sources.In the theoretical analysis part,passive Q-switching technology was analyzed,and the related properties of Cr⁴⁺:YAG,SnSe₂,PdSe₂,and ReS₂ were studied,then the morphological characteristics of the latter three nanosheets were investigated.Next,the continuous output performance and pulse laser performance of the two crystals were explored.The corresponding continuous output performance was studied based on two pumping methods.After optimization,the output power and slope efficiency were compared in the best state,and then investigate the two methods of output spot profile and M2 factor by CCD.Then the beam quality of the two pumping modes was investigated by means of the output spot profile and M2 factor captured by the CCD.Next,passive Q-switching was performed based on the direct pumping method.Cr⁴⁺:YAG was inserted into the cavity for passive Q-switching,and the relevant performance parameters of the output laser were measured.Then SnSe₂,PdSe₂ and ReS₂ nanosheets were add for Q-switching and the pulse performances of the output laser were measured,respectively.Based on comprehensive experimental data,this paper compared the continuous passive performance of Nd:GdNbO₄ and Nd:GdTaO₄,and proved that the direct pumping method would obtain greater output power and slope efficiency,and can improve the laser beam quality.The morphological characteristics of SnSe₂,PdSe₂ and ReS₂ nanosheets were studied,and their thickness distribution,Raman spectrum and transmittance were obtained.In the Q-switching experiment using 879 nm direct pumping,Cr⁴⁺:YAG with low transmittance had greater pulse energy and peak power.Then three kinds of nanosheets were used to achieve passive Q-switching respectively,it can be found that ReS₂ nanosheets can output the highest pulse energy and peak power,corresponding to the maximum modulation depth.