Inoue Hyuga, Mine Sota, Kawase Kodo, Murate Kosuke
Department of Electronics, Graduate school of Engineering, Nagoya University, Furocho, Chikusa, Nagoya, 4648603, Japan.
Sci Rep. 2025 Jul 1;15(1):20995. doi: 10.1038/s41598-025-06264-7.
In the THz parametric detection method, which detects terahertz (THz) waves by upconverting them to a near-infrared beam in a LiNbO crystal, it has been widely assumed that the THz waves and the pump beam must satisfy the non-collinear phase-matching condition, dictated by the law of momentum conservation, and that the incidence angle of the THz waves to the crystal must be precisely controlled. However, in this study, we discovered that THz waves can be detected even at various incidence angles to the LiNbO crystal that do not satisfy the non-collinear phase-matching condition. While the incidence angle tolerance for the near-infrared injection beam during THz wave generation is as narrow as 0.058 degrees, a remarkably large tolerance of approximately 116 degrees was achieved for terahertz detection. This finding also indicates that the Si prism coupler, previously considered essential for satisfying the phase-matching condition, is not necessarily required. The large incidence-angle tolerance significantly simplifies the optical setup and opens up possibilities for a wider range of application measurements.
在太赫兹参量检测方法中，该方法通过在铌酸锂晶体中将太赫兹（THz）波上转换为近红外光束来检测太赫兹波，人们普遍认为太赫兹波和泵浦光束必须满足由动量守恒定律决定的非共线相位匹配条件，并且太赫兹波对晶体的入射角必须精确控制。然而，在本研究中，我们发现即使太赫兹波对铌酸锂晶体的入射角不满足非共线相位匹配条件，也能检测到太赫兹波。虽然在太赫兹波产生过程中，近红外注入光束的入射角容差窄至0.058度，但在太赫兹检测中却实现了约116度的显著大容差。这一发现还表明，先前认为满足相位匹配条件必不可少的硅棱镜耦合器不一定是必需的。大入射角容差显著简化了光学装置，并为更广泛的应用测量开辟了可能性。
