Seo Meenkyo, Mun Je-Hoi, Heo Jaeuk, Kim Dong Eon
Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 37673, South Korea.
Max Planck POSTECH/KOREA Research Initiative, Pohang, 37673, South Korea.
Sci Rep. 2022 Sep 29;12(1):16273. doi: 10.1038/s41598-022-20622-9.
Dynamic control of material properties using strong-field, narrowband THz sources has drawn attention because it allows selective manipulation of quantum states on demand by coherent excitation of specific low-energy modes in solids. Yet, the lack of powerful narrowband lasers with frequencies in the range of a few to a few tens of THz has restricted the exploration of hidden states in condensed matter. Here, we report the optimization of an optical parametric amplifier (OPA) and the efficient generation of a strong, narrowband THz field. The OPA has a total conversion efficiency of > 55%, which is the highest value reported to date, with an excellent energy-stability of 0.7% RMS over 3 h. We found that the injection of a high-energy signal beam to a power amplification stage in an OPA leads to high-efficiency and a super-Gaussian profile. By difference-frequency generation of two chirped OPA signal pulses in an organic nonlinear crystal, we obtained a THz pulse with an energy of 3.2 μJ, a bandwidth of 0.5 THz, and a pulse duration of 860 fs tunable between the 4 and 19 THz regions. This corresponds to an internal THz conversion efficiency of 0.4% and a THz field strength of 6.7 MV/cm. This approach demonstrates an effective way to generate narrow-bandwidth, intense THz fields.
利用强场窄带太赫兹源对材料特性进行动态控制已引起关注，因为它能够通过对固体中特定低能模式的相干激发按需选择性地操纵量子态。然而，缺乏频率在几太赫兹到几十太赫兹范围内的强大窄带激光器限制了对凝聚态物质中隐藏态的探索。在此，我们报告了光学参量放大器（OPA）的优化以及强窄带太赫兹场的高效产生。该OPA的总转换效率大于55%，这是迄今为止报道的最高值，在3小时内具有0.7% RMS的出色能量稳定性。我们发现，向OPA中的功率放大级注入高能信号光束可实现高效率和超高斯分布。通过在有机非线性晶体中对两个啁啾OPA信号脉冲进行差频产生，我们获得了一个太赫兹脉冲，其能量为3.2 μJ，带宽为0.5 THz，脉冲持续时间为860 fs，可在4至19 THz区域之间调谐。这对应于0.4%的内部太赫兹转换效率和6.7 MV/cm的太赫兹场强。这种方法展示了一种产生窄带宽、高强度太赫兹场的有效途径。
