Multi-octave MV/cm pulses filling the THz gap

Single-cycle THz pulses with electric field strength of MV/cm are required for wide range of applications from physics to biology and medicine [1]. Presently, high fields are still challenging to produce in the THz gap (0.1-10 THz) where important condensed matter resonances are expected (i.e. magnons, phonons, electromagnons). We present our latest results on the generation of 1.5 MV/cm electric field in this frequency range. Broadband THz pulse are achieved by optical rectification (OR) in large organic crystals such as DAST, OH1 and DSTMS [2-4]. These materials present an OR susceptibility one order of magnitude larger than the room-temperature inorganic nonlinear crystals. The THz radiation is phase-matched with IR pump allowing for photon conversion larger than 200% and pulse energy of tens of μJ. The beam can be focused to nearly diffraction-limit for the realization of the highest field. For 0.5 mm thick DSTMS, electric field larger than 1.5 MV/cm is achieved in 350 μm FWHM spot. The electro-optical sampling trace, the corresponding 5-octave spectrum (0.15-5 THz) and the THz focus are shown in Fig. 1. Fields of the 1 MV/cm are obtained also in DAST and OH1. We show that proper dispersive materials can be used to control absolute phase of the THz transient without significant losses.