Research On Q-switched Laser Characterisics Of Novel Mixed Crystal Nd:GdYTaO₄ And Nd:GdYNbO₄

Solid-state lasers have a wide range of applications in laser processing,laser radar and optoelectronic countermeasures.As an important part of lasers,laser media is the core and foundation of laser technology development.It is of great significance to study the laser output characteristics of new laser crystals.The new mixed crystals Nd:GdYTaO₄and Nd:GdYNbO₄ studied in this paper are suitable for the output of 1066 nm laser and have the potential of high-performance,high-repetition pulse laser output.In the perspective of alleviating the thermal effect,the Q-switched lasers output characteristics of the new mixed crystal Nd:GdYTaO₄ and Nd:GdYNbO₄ were studied by direct pumping.In this paper,the thermal effects,indirect pumping technology and direct pumping technology of laser medium are introduced.Direct pumping technology is used to directly pump the ground state particles to the upper level of the laser,which can effectively alleviate the thermal effect of crystal.Theoretical calculations show that the thermal load is reduced by about 27.3%with 879 nm instead of 808 nm pumping.The simulation and experimental results are basically consistent.The feasibility of direct pumping of Nd:GdYTaO₄ and Nd:GdYNbO₄ crystals was studied.The laser output performance of the indirect pumped 808 nm LD and the direct pumped 879 nm LD was compared.When the 879 nm LD is used instead of the 808 nm LD pump,the maximum continuous output power of the Nd:GdYTaO₄ laser is increased from 5.1 W to 9 W.The maximum continuous output power of the Nd:GdYNbO₄ laser is increased from 2.1 W to 6 W.In the acousto-optic Q-switched laser experiment,the single-pulse energy,pulse width,and peak power of the Nd:GdYTaO₄ laser are increased from 47.5?J,34.8 ns,and 1.4 kW to 93.5?J,20 ns,and 4.7 kW when the output frequency is 20 kHz.The single pulse energy,pulse width,and peak power of the Nd:GdYNbO₄laser increased from 41?J,24.5 ns,and 1.68 kW to 75.7?J,17.5 ns,and 4.25 kW.The879 nm LD direct pumping method can effectively improve the continuous and pulse output performance of Nd:GdYTaO₄ and Nd:GdYNbO₄.In the study of passive Q-switched lasers,in order to further reduce the thermal effect of the crystal,a pulse pumping method is employed.When the passive Q-switched crystal is not added,the pump frequency is 1 kHz,the pump pulse width is 200?s,the Nd:GdYTaO₄ crystal absorbs the pump energy by 7.2 mJ,the maximum output energy is4.1 mJ,and the slope efficiency is 58.5%.The Nd:GdYNbO₄ laser absorbs pump energy of 5.79 mJ,the maximum output energy is 2.47 mJ,and the slope efficiency is 48.7%.Compared with continuous pumping of 879 nm LD,the pulse pumping method has improved the conversion efficiency and slope efficiency of the laser.When the initial transmittance of Cr⁴⁺:YAG is 50%,the Nd:GdYTaO₄ laser has 1 pulse in each pumping cycle,and obtains laser output with single pulse energy of 151?J,pulse width of 7 ns,and peak power of 21.6 Kw.Nd:The GdYNbO₄ laser has 7 pulses per pump cycle and a maximum repetition rate of 38.2 kHz.It achieves single pulse energy of 158?J,pulse width of 5 ns,and peak power of 31.6 kW.When the initial transmittance of Cr⁴⁺:YAG is90%,the Nd:GdYTaO₄ laser achieves the highest repetitive frequency of 116.6 kHz,and the Nd:GdYNbO₄ laser achieves the highest repetitive frequency of 127.5 kHz,which has the potential of high repetitive pulse output.