Bridger M, Naranjo-Montoya O A, Tarasevitch A, Bovensiepen U
Opt Express. 2019 Oct 28;27(22):31330-31337. doi: 10.1364/OE.27.031330.
High-energy femtosecond laser pulses in the mid-infrared (MIR) wavelength range are essential for a wide range of applications from strong-field physics to selectively pump and probe low energy excitations in condensed matter and molecular vibrations. Here we report a four stage optical parametric chirped pulse amplifier (OPCPA) which generates ultrashort pulses at a central wavelength of 3000 nm with 430 J energy per pulse at a bandwidth of 490 nm. Broadband emission of a Ti:sapphire oscillator seeds both the four stage OPCPA 800 nm and the pump line at 1030 nm. The first stage amplifies the 800 nm pulses in BBO using a non-collinear configuration. The second stage converts the wavelength to 1560 nm using difference frequency generation in BBO in a collinear geometry. The third stage amplifies this frequency non-collinearly in KTA. Finally, the fourth stage generates the 3000 nm radiation in a collinear configuration in LiIO due to the broad amplification bandwidth this crystal provides. We compress these pulses to 65 fs by transmission through sapphire. Quantitative calculations of the individual non-linear processes in all stages verify that our OPCPA architecture operates close to optimum efficiency. Low absorption losses suggest that this particular design is very suitable for operation at high average power and multi kHz repetition rates.
中红外（MIR）波长范围内的高能飞秒激光脉冲对于从强场物理到选择性泵浦和探测凝聚态物质中的低能激发以及分子振动等广泛应用至关重要。在此，我们报道了一种四级光学参量啁啾脉冲放大器（OPCPA），它能在中心波长3000 nm处产生超短脉冲，每个脉冲能量为430 J，带宽为490 nm。钛宝石振荡器的宽带发射为四级OPCPA的800 nm和1030 nm的泵浦光提供种子光。第一级在BBO中采用非共线配置放大800 nm脉冲。第二级在BBO中采用共线几何结构通过差频产生将波长转换为1560 nm。第三级在KTA中对该频率进行非共线放大。最后，由于LiIO晶体提供的宽放大带宽，第四级在LiIO中采用共线配置产生3000 nm辐射。我们通过蓝宝石传输将这些脉冲压缩至65 fs。对所有级中各个非线性过程的定量计算证实，我们的OPCPA架构接近最佳效率运行。低吸收损耗表明这种特定设计非常适合高平均功率和多千赫兹重复率运行。
