Cascaded terahertz parametric generation under noncollinear phase matching condition

Abstract

Abstract In our study, we directly observed terahertz (THz) waves generated through a cascade process utilizing a noncollinear phase matching condition in a THz parametric generator. Although there has been extensive research into cascade processes using collinear phase matching, studies focusing on cascade processes with noncollinear phase matching, such as our injection-seeded THz parametric generator (is-TPG), have been less common. However, understanding the cascade process in is-TPG is not only crucial for the development of THz-wave sources but also holds significance for THz parametric detection and amplification, and there has been a demand for its direct observation. In this research, using a high-power seed beam, we efficiently induced the cascade process, and by tilting the crystal, we were able to detect higher-order THz-waves near the end face that had not been observed before. To the best of our knowledge, no previous studies have observed THz-waves generated by a cascade process under noncollinear phase matching conditions. Our findings provide vital empirical data for the theoretical examination of THz parametric generation. We anticipate that this study will pave the way for future research aimed at enhancing the output power of THz sources.