不同切割方向Ho...YAP晶体激光输出特性的实验研究

Experimental Investigation of Laser Output Characteristics of Ho…YAP Crystal in Different Cutting Directions

不同切割方向的Ho…YAP晶体的激光输出特性存在差别。针对掺杂浓度为0.5%(原子数分数)的Ho…YAP晶体开展a、b、c三种切割方向的激光输出特性实验研究。采用最大输出功率为44.3W的1915nm掺铥光纤激光器端面泵浦Ho…YAP晶体,在三种切割方向上均获得了大于20 W的连续激光输出,其中b向切割晶体输出激光的中心波长近2118nm,最大功率为23.6W,斜率效率为61.98%,a向切割晶体与b向切割晶体的输出结果相近,c向切割晶体在达到最大输出功率时的中心波长为2129nm;当采用腔内声光调Q获得脉冲输出时,a、c向切割晶体出现了中心波长偏移和多波长起振现象,而b向切割晶体则获得了中心波长近2118nm的稳定脉冲输出,且其在重复频率为20kHz时的最大平均输出功率为22.3W,脉宽为20ns,斜率效率为55.22%,光束质量因子分别为M^2_x=1.81和M^2_y=1.50。选用b向切割的Ho…YAP晶体更有利于实现稳定且高效的2118nm连续激光及纳秒级脉冲激光输出。

The laser output characteristics of Ho…YAP crystal are discrepant along different cutting directions.In this study,a-cut,b-cut,and c-cut 0.5%(atomic fraction)Ho…YAP crystals were used to investigate laser output characteristics.Using a thulium-doped fiber laser with a central wavelength of 1915 nm and maximum power of44.3 Wto end pump the Ho…YAP crystal along each cutting direction,continuous-wave laser power greater than20 W was achieved.For the b-cut crystal,the central wavelength of the output laser is close to 2118 nm and the maximum continuous-wave output power and slope efficiency are 23.6 Wand 61.98%,respectively.The results for the a-cut crystal are similar to those for the b-cut crystal,but the central wavelength for the c-cut crystal is 2129 nm when the maximum output laser power is achieved.When the Ho…YAP laser operates in an in-cavity acousticoptical Q-switched state,central wavelength shifting and multi-wavelength resonance occur in the a-cut and c-cut crystals.However,for the b-cut crystal,a stable pulsed laser output with a central wavelength close to 2118 nm can be obtained.For a pulse repetition rate of 20 kHz,the maximum average output power,pulse width,slope efficiency,and beam quality factor are 22.3 W,20 ns,55.22%,M^2_x=1.81,and M^2_y=1.50,respectively.From these results,it can be concluded that the b-cut Ho…YAP crystal is more suitable for obtaining stable and efficient2118-nm continuous-wave lasers and nanosecond-level pulsed laser output.