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