High-efficiency near-infrared optical parametric amplifier for intense, narrowband THz pulses tunable in the 4 to 19 THz region

• Published in: Scientific reports 2022-09, Vol.12 (1), p.16273-16273, Article 16273
• Main Authors: Seo, Meenkyo, Mun, Je-Hoi, Heo, Jaeuk, Kim, Dong Eon
• Format: Article
• Language: English
• Subjects: 639/624; 639/624/1020; 639/624/1107; 639/624/400; Efficiency; Energy; Humanities and Social Sciences; Lasers; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• 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.