Efficient Generation of Intense Broadband Terahertz Pulses from Quartz

The intense terahertz (THz) pulses facilitate the observation of various nonlinear optical effects and manipulation of material properties. In this work, we report a convenient approach that can produce strong broadband terahertz pulses with center frequency tunable between 2-4 THz. The coherent THz light source with pulse energy of 1.2 microjoule can be generated from a low-cost crystalline quartz pumped by an ultrashort tilted wave-front pulse. Thanks to the wide transparent spectral window and high damage threshold, our theoretical analysis and experiment show that the optical rectification in quartz is as efficient as that in LiNbO3, but covers much broader spectral range. This work not only provides the light source that is urgently needed for nonlinear THz spectroscopy beyond 1 THz, but offers an alternative route in the selection of nonlinear optical crystals for optical frequency conversion.