Heiner Zsuzsanna, Petrov Valentin, Panyutin Vladimir L, Badikov Valeriy V, Kato Kiyoshi, Miyata Kentaro, Mero Mark
School of Analytical Sciences Adlershof, Humboldt-Universität zu Berlin, 12489, Berlin, Germany.
Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, 12489, Berlin, Germany.
Sci Rep. 2022 Mar 24;12(1):5082. doi: 10.1038/s41598-022-08964-w.
Nonlinear vibrational spectroscopy profits from broadband sources emitting in the molecular fingerprint region. Yet, broadband lasers operating at wavelengths above 7 μm have been lacking, while traditional cascaded parametric frequency down-conversion schemes suffer from exceedingly low conversion efficiencies. Here we present efficient, direct frequency down-conversion of femtosecond 100-kHz, 1.03-μm pulses to the mid-infrared from 7.5 to 13.3 μm in a supercontinuum-seeded, tunable, single-stage optical parametric amplifier based on the wide-bandgap material CdHgGaS. The amplifier delivers near transform-limited, few-cycle pulses with an average power > 30 mW at center wavelengths between 8.8 and 10.6 μm, at conversion efficiencies far surpassing that of optical parametric amplification followed by difference-frequency generation or intrapulse difference-frequency generation. The pulse duration at 10.6 μm is 101 fs corresponding to 2.9 optical cycles with a spectral coverage of 760-1160 cm. CdHgGaS is an attractive alternative to LiGaS and BaGaS in small-scale, Yb-laser-pumped, few-cycle mid-infrared optical parametric amplifiers and offers a much higher nonlinear figure of merit compared to those materials. Leveraging the inherent spatial variation of composition in CdHgGaS, an approach is proposed to give access to a significant fraction of the molecular fingerprint region using a single crystal at a fixed phase matching angle.
非线性振动光谱得益于在分子指纹区发射的宽带光源。然而，波长在7μm以上的宽带激光器一直缺乏，而传统的级联参量频率下转换方案的转换效率极低。在此，我们展示了一种基于宽带隙材料CdHgGaS的超连续谱种子注入、可调谐、单级光学参量放大器，可将飞秒100kHz、1.03μm脉冲高效直接下转换为7.5至13.3μm的中红外光。该放大器在中心波长8.8至10.6μm之间输出近变换极限、少周期脉冲，平均功率>30mW，转换效率远远超过先进行光学参量放大再进行差频产生或脉冲内差频产生的情况。10.6μm处的脉冲持续时间为101fs，对应2.9个光学周期，光谱覆盖范围为760 - 1160cm。在小规模、镱激光泵浦、少周期中红外光学参量放大器中，CdHgGaS是LiGaS和BaGaS的一种有吸引力的替代材料，与这些材料相比，它具有更高的非线性品质因数。利用CdHgGaS中成分固有的空间变化，提出了一种方法，通过在固定相位匹配角下使用单晶来覆盖分子指纹区的很大一部分。
