Research On Continuous Wave And Pulsed Laser Characteristics Of Yb:LuPO₄ Crystal

Due to their extremely high chemical stability,tetragonal rare-earth orthophosphates are very promising for applications as ideal host materials for trivalent rare-earth active ions,to develop new laser crystals with excellent performances.In this work we carried out a comprehensive systematic experimental investigation into the continuous-wave laser properties,passive Q-switching and acousto-optic Q-switching pulsed laser characteristics of Yb-ion doped thin-plate or miniature-rod shaped lutetium orthophosphate?Yb:LuPO₄?crystals,which were developed in recent years,and could be grown by high-temperature solution method.Through this investigation,a series of research results of significance of innovation were achieved.Highly efficient continuous-wave and passively Q-switched operation of an Yb:LuPO₄ microchip laser was realized by use of a 0.3-mm thin-plate crystal.With 2.37W of pump power absorbed in the crystal,a continuous-wave output power of 1.45 W was produced with a slope efficiency as high as 73%.In passively Q-switched laser operation with a Cr⁴⁺:YAG crystal serving as saturable absorber,the maximum average output power reached 0.53 W,the resulting single pulse energy,duration,and peak power were 22.3?J,4.0 ns,and 5.6 kW,respectively.With the help of a simple plano-concave resonator,a passively Q-switched Yb:LuPO₄ miniature crystal rod laser operating in 1005.0-1012.5 nm spectral region was demonstrated under diode longitudinal pumping conditions.At pulse repetition frequency of 166.7 kHz,the average output power produced could reach 7.2 W,the corresponding optical-to-optical and slope efficiencies were,respectively,38.5%and 45%.With still higher output coupling and still lower initial transmission of saturable absorber,an average output power of 2.9 W was generated at 19.2 kHz,the pulse energy,duration,and peak power were 151?J,3.0 ns,and 50.3 kW,respectively.Acousto-optically Q-switched laser action in 1000-1010 nm range was achieved with a miniature crystal rod of Yb:LuPO₄,over a wide repetition-rate range of 1-50 kHz.The highest average output power was generated at repetition rate of 50 kHz,reaching6.55 W with a slope efficiency of 40%;while at a low repetition rate of 2 kHz,the average output power could also reached 1.43 W,with pulse energy,duration,and peak power being 0.715 mJ,12.5 ns,and 57.2 kW,respectively.