Optical rectification and electro-optic sampling in quartz

We report the electro-optic sampling (EOS) response and the terahertz (THz) optical
rectification (OR) of the z-cut α-quartz. Due to its small effective second-order nonlinearity, large
transparency window and hardness, freestanding thin quartz plates can faithfully measure the
waveform of intense THz pulses with MV/cm electric-field strength. We show that both its OR
and EOS responses are broad with extension up to ∼8 THz. Strikingly, the latter responses are
independent of the crystal thickness, a plausible indication of dominant surface contribution to
the total second-order nonlinear susceptibility of quartz at THz frequencies. Our study introduces
the crystalline quartz as a reliable THz electro-optic medium for high field THz detection, and
characterize its emission as a common substrate.