Phase-locked generation and field-resolved detection of widely tunable terahertz pulses with amplitudes exceeding 100 MV/cm

Phase-locked terahertz transients with peak electric fields of 108 MV/cm and center frequencies continuously tunable from 10 to 72 THz are generated via difference-frequency mixing of two parametrically amplified pulse trains from a single white-light seed. Free space electro-optic sampling with 8 fs gating pulses from a two-branch Er:fiber laser allows us to monitor all transients directly in the time domain. We identify extreme terahertz nonlinearities in the detector crystal with subcycle resolution. (C) 2008 Optical Society of America