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.
Original publication
Narrow-band and tunable intense terahertz pulses for mode-selective coherent phonon excitation. C. Vicario, A. Trisorio, S. Allenspach, C. Rüegg, and F. Giorgianni. Appl. Phys. Lett. 117, 101101 (2020); https://doi.org/10.1063/5.0015612