Efficient generation of intense broadband terahertz pulses from quartz

Abstract

Intense terahertz (THz) pulses facilitate the observation of various nonlinear optical effects and the manipulation of material properties. In this work, we report a convenient approach to produce strong broadband THz pulses with a center frequency tunable between 2 and 4 THz. A coherent THz light source with a pulse energy of 1.2 mJ can be generated from low-cost crystalline quartz using a tilted-pulse-front scheme. Thanks to the wide transparent spectral window and high damage threshold, our theoretical analysis and experiment show that the THz conversion efficiency in quartz reaches 0.05%, which is comparable with that in LiNbO3 at room temperature, while the output THz spectral range is much broader in the former. This work not only provides the light source that is urgently needed for nonlinear THz spectroscopy beyond 2 THz but also offers an alternative route in selecting nonlinear optical crystals for optical frequency conversion.