In nonlinear optical (NLO) crystals, the selection of pump light wavelengths for the generation of terahertz (THz) waves is limited due to problems associated with coherence length, refractive index, and absorption by the crystal. Relaxation of this limitation would open up potential light sources for THz generation. One such solution, Cherenkov phase matching, removes the coherence length constraint. In this study, we attempted to generate THz waves from an NLO crystal using femtosecond pulses of various wavelengths. Specifically, 805-nm and 1560-nm femtosecond pulses were used to pump a prism-coupled ${\mathrm{LiNbO}}_3$ crystal. Broadband THz-wave generation and a THz-wave output proportional to the square of the pump light intensity were observed at both wavelengths. The generation of THz waves by prism-coupled Cherenkov phase matching was not limited by the wavelength of the pump light. Moreover, THz-wave generation at even greater intensities may be possible by optimizing the pump source and coupling to an NLO crystal.

中文翻译：

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非线性光学晶体产生与泵浦波长无关的宽带太赫兹

在非线性光学（NLO）晶体中，由于与晶体的相干长度，折射率和吸收有关的问题，限制了用于产生太赫兹（THz）波的泵浦光波长的选择。放宽此限制将为THz产生打开潜在的光源。一种这样的解决方案，即Cherenkov相位匹配，消除了相干长度约束。在这项研究中，我们尝试使用各种波长的飞秒脉冲从NLO晶体产生THz波。具体来说，使用805 nm和1560 nm飞秒脉冲来泵浦棱镜耦合${\mathrm{铌酸锂}}_3$水晶。在两个波长下都观察到宽带太赫兹波的产生和与泵浦光强度的平方成正比的太赫兹波的输出。通过棱镜耦合的契伦科夫相位匹配产生的太赫兹波不受泵浦光波长的限制。此外，通过优化泵浦源并耦合至NLO晶体，甚至可以产生更高强度的太赫兹波。