基于光子晶体光纤飞秒激光技术的高功率紫外激光源

实验研究了一种基于大模场面积光子晶体光纤飞秒激光技术的紫外飞秒激光源.分析了群速失配下的倍频光和基频光的走离长度,并实验比较了不同长度的BBO晶体的倍频功率和效率.分别采用5 mm和0.18 mm的两块BBO晶体,在Ⅰ类相位匹配条件下,对光子晶体光纤放大器输出的脉宽为110 fs,重复频率50 MHz的1040 nm飞秒激光进行腔外二倍频(SHG)和四倍频(FHG),获得了高功率紫外飞秒激光.在20 W的平均功率抽运下,获得了8.88 W的二倍频绿光输出,转换效率为44.4%.同时获得了656 mW的四倍频260 nm紫外激光,单脉冲能量13 nJ,最高功率时二次谐波(SH)到四次谐波(FH)的转换效率为7.39%.

High Power Ultraviolet Laser Source Based on Photonic Crystal Fiber Femtosecond Laser System

A novel ultraviolet (UV) femtosecond laser source is experimentally studied based on the large-mode-area photonic crystal fiber femtosecond laser system. Walk-off effecting due to the group velocities mismatch between the fundamental wave and the second harmonic is analyzed theoretically. The average power and the conversion efficiency of second harmonic generation with different crystal length are compared experimentally. Second harmonic generation (SHG) and fourth harmonic generation (FHG) of 1040 nm fundamental wave are demonstrated, and high power UV femtosecond laser is obtained out of cavity at the repetition rate of 50 MHz by using two pieces of Type-Ⅰ BBO crystal, length of which is 5 mm and 0.18 mm respectively. The fundamental wave is generated from the photonic crystal fiber amplifier with pulses duration of 110 fs. At the average power of 20 W, 8.88 W frequency doubled green laser wave is obtained with the conversion efficiency up to 44.4%, and 656 Mw FHG UV laser is also achieved with a single pulse energy of 13 Nj. The conversion efficiency from the second harmonic (SH) to the fourth harmonic (FH)is up to 7.39%at the maximum power.