We generate frequency-tunable narrow-band intense fields in the terahertz (THz) range by optical rectification of a temporally modulated near-infrared laser pumping a nonlinear organic crystal. Carrier-frequency tunability between 0.5 and 6.5 THz is achieved by changing the modulation period of the laser pump. This tunable narrow-band THz source allows the selective coherent excitation of adjacent vibrational modes, which are demonstrated for two phonons with a frequency offset of 0.8 THz in single-crystal SrCu2(BO3)2. Our compact and scalable source enables an effective approach for the advanced manipulation of low-energy collective modes in condensed matter and has the potential to reveal the coupling of specific lattice vibrations with other degrees of freedom.

中文翻译：

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用于模式选择相干声子激发的窄带和可调强太赫兹脉冲

我们通过泵浦非线性有机晶体的时间调制近红外激光的光学整流，在太赫兹 (THz) 范围内产生频率可调的窄带强场。0.5 到 6.5 THz 之间的载频可调性是通过改变激光泵的调制周期来实现的。这种可调谐窄带太赫兹源允许对相邻振动模式进行选择性相干激发，这在单晶 SrCu2(BO3)2 中频率偏移为 0.8 THz 的两个声子中得到了证明。我们紧凑且可扩展的源能够为凝聚态物质中的低能集体模式的高级操纵提供一种有效的方法，并有可能揭示特定晶格振动与其他自由度的耦合。