长脉宽大能量Yb∶YAG平面波导激光放大器

Long Pulse Laser Amplification of Yb∶YAG Planar Waveguide with High Energy

搭建了1030 nm波长的准连续长脉宽室温Yb∶YAG平面波导激光放大器,分析对比注入光强、抽运光强和抽运脉宽等因素对光-光转换效率的影响。采用主振荡功率放大结构,种子源为1030 nm连续保偏光纤激光器。放大器增益介质为一块Yb∶YAG平面波导,抽运源为两个准连续940 nm半导体激光阵列,抽运光经整形后分别从两个端面耦合进入平面波导。在双端抽运下,抽运重复频率为400 Hz和最大峰值功率为20.4 kW时获得了最大能量为4.65 J的激光放大输出,偏振度为97%,光-光转换效率为44.0%,与理论分析基本吻合。

Objective Diode-pumped solid-state laser(DPSSL)has a large energy compact structure,high efficiency,and good stability,which possesses outstanding application value and prospects in scientific research,military,industrial processing,and other fields.DPSSL has achieved rapid development in the past 10 years.The efficiency of high average-power solid-state laser has been the development direction of solid-state lasers.The planar waveguide gain medium can satisfy the high injected laser and high pump laser intensities.Thus,the planar waveguide laser is one of the potential laser technologies for obtaining high optical-optical efficiency and high average-power output.In this study,aquasi-continuous long pulse width Yb∶YAG planar waveguide laser amplifier at room temperature with a wavelength of 1030 nm was constructed and the factors affecting the optical-optical conversion efficiency were analyzed.We hope that this study will help improve the optical-optical conversion efficiency of high-power solidstate lasers.Methods The experiment is based on a planar waveguide gain medium.First,the theoretical model of laser dynamics based on Yb∶YAG was developed.The effects of the injected laser intensity,pump laser intensity,and pump pulse width on the optical-optical conversion efficiency were analyzed through computer simulation.Then,a quasi-continuous long pulse width Yb∶YAG planar waveguide laser amplifier at room temperature with a wavelength of 1030 nm was constructed.Next,the output energy of the amplifier was tested to verify the correctness of the theoretical model.The laser amplifier was operated at different pulse repetition frequencies.In addition,the beam quality of the output laser was measured using a beam quality analyzer,and spectra of the output laser were analyzed using a spectrograph.Results and Discussions The simulation results show that the higher the seed laser power,the earlier it enters the steady-state extraction.The higher the injected laser intensity,the higher the optical efficiency of the steady-state and optical-optical efficiency of the pulse.However,the increase in steady-state optical-optical efficiency decreases gradually(Table 1).With an increase in pump power,the steady-state optical-optical efficiency increases and remains stable.Due to the shortening of power rise time,the optical-optical efficiency of the single pulse increases(Table 2).The output power of the pulse width of 500μs and output power pulse width of 1 ms are identical in the first 500μs,indicating that the pump pulse width does not affect the time to reach a steady-state(Fig.6).The time to reach a steady-state is decided by the pump and injection intensities.The pump pulse width is longer,proportion of the time to reach a steady-state in the entire pulse width is smaller,and pulse optical-optical efficiency approaches the steady-state optical-optical efficiency.The theoretical calculation results show that the output energy is 4.96 Jand optical efficiency of monopulse is 46.8%,when pulse width is 500μs.The experimental result shows that the output energy is 4.67 Jand optical-optical efficiency is 44.0%(Fig.7),which is consistent with the theoretical calculation result.The single pulse energy of the laser is not affected by pulse repetition frequency.Thus,the average output power can be linearly increased by increasing the repetition frequency.With the average output power increasing,the beam quality of the output laser gets worse in the Y direction(Figs.8--10).The amplified output laser has the same central wavelength as the seed laser,but the linewidth is slightly compressed(Fig.11).Conclusions In this study,aquasi-continuous long pulse width Yb∶YAG planar waveguide laser amplifier at room temperature with a wavelength of 1030 nm is constructed.The effects of injected laser intensity,pump laser intensity,and pump pulse width on the optical-optical conversion efficiency are analyzed.The master oscillator power amplifier is adopted,and the seeder is maintained at a polarization of 1030 nm fiber laser.The gain medium of the amplifier is a Yb∶YAG planar waveguide,and the pump sources are two quasi-continuous 940 nm laser diode arrays.After shaping,the pump light is coupled into the planar waveguide from the two end facets.With dual end pumping,we obtain the laser amplification output with a maximum energy of 4.65 Jwhen the pump repetition frequency is 400 Hz,and the maximum peak pump power is 20.4 kW.The polarization degree is 97%,and the optical-optical conversion efficiency is 44.0%,which is consistent with the theoretical calculation.