Room temperature operated very small widely tunable terahertz parametric source

我们研究了基于MgO：LiNbO_3晶体极化激元模散射的太赫兹波参量振荡器（TPO）和太赫兹波参量发生器（TPG）[2]。TPO已被证明是一个有用的相干太赫兹波源，在室温下工作。它可以在100至300 μm（1至3 THz）范围内连续调谐，并且可以发射高达几十mW的峰值功率。TPO和TPG之间的区别在于前者有闲频腔，而后者没有。传统TPG的太赫兹波线宽超过1 THz，输出比TPO小得多。通过向闲频注入种子，TPG谱被窄化到脉冲宽度的傅里叶变换极限。太赫兹波的线宽从>1太赫兹急剧锐化到100兆赫。利用外腔半导体激光器作为注入种子，在0.7 ~ 2.4THz（波长125 ~ 430 μm）范围内观察到了宽调谐范围。在低压水蒸气吸收光谱中验证了is-TPG的连续扫描和窄光谱带宽。同时，所获得的输出比常规TPG、TPO和is-TPO更稳定。据我们所知，注入种子到纳秒光参量发生器（OPG）直到最近才被报道，由于参量增益的限制。

We have researched a THz-wave parametric oscillator (TPO) and THz-wave parametric generator (TPG) based on the polariton mode scattering of MgO : LiNbO_3 crystals [2]. The TPO has proved to be a useful coherent THz-wave source that operates at room temperature. It is continuously tunable in the 100 to 300 μm (1 to 3 THz) range in one operation and can emit peak powers of up to several tenths mW. The difference between a TPO and a TPG is that the former has an idler cavity while the latter does not. The THz-wave linewidth of a conventional TPG exceeds 1 THz and the output is much smaller than that from a TPO. The TPG spectrum was narrowed to the Fourier transform limit of the pulsewidth by introducing an injection seeding to the idler. The THz-wave linewidth was dramatically sharpened from >1 THz to 100 MHz. A wide tunability from 0.7 to 2.4 THz (wavelength : 125 to 430 μm) was observed using an external cavity diode laser as an injection seeder. The continuous scanning and narrow spectral bandwidth of the is-TPG were verified in the absorption spectrum of low-pressure water vapor. Simultaneously, the output obtained was more stable than that from conventional TPG, TPO, and is-TPO. As far as we know, injection seeding to ns optical parametric generators (OPG) has not been reported until recently, due to the limit of parametric gain.