Institue of Laser Engineering, Osaka University, Suita, Osaka, Japan.
Opt Lett. 2013 Mar 15;38(6):953-5. doi: 10.1364/OL.38.000953.
We present a simple scheme of narrowband terahertz (THz) generation by optical rectification in the lithium niobate crystal covered by a binary phase mask. It is shown that a single-domain crystal illumination by spatiotemporal shaped fs-laser pulses is equivalent to the formation of a transversally patterned, quasi-phase-matching structure. Decrease of the optical beam size on the mask leads to an increase of the THz-wave linewidth from 17 GHz to a few THz. The frequency of the generation was tuned in the range of 0.4-1.0 THz by building images of the mask in the crystal with various magnifications. Application results of the presented THz source for measuring transmittance of the superconducting NbN thin film in the 4.2-15 K temperature range are also presented.
我们提出了一种通过在铌酸锂晶体上覆盖二元相位掩模进行光整流产生窄带太赫兹（THz）的简单方案。结果表明，用时空整形的飞秒激光脉冲对单畴晶体进行照明相当于形成了一个横向图案化的准相位匹配结构。在掩模上减小光束尺寸会导致 THz 波线宽从 17GHz 增加到几个 THz。通过在晶体中以不同的放大倍数构建掩模图像，将产生的频率调谐在 0.4-1.0THz 范围内。还介绍了所提出的 THz 源在测量超导 NbN 薄膜在 4.2-15K 温度范围内的透过率方面的应用结果。
