Lawrence Berkeley National Laboratory

We report the generation of ultrabroadband pulses spanning the 50-130 THz frequency range via phase-matched difference frequency mixing within the broad spectrum of sub-10 fs pulses in LiIO_3. Model calculations reproduce the octave-spanning spectra and predict few-cycle THz pulse durations less than 20~;fs. The applicability of this scheme is demonstrated with 9-fs pulses from a Ti:sapphire oscillator and with 7-fs amplified pulses from a hollow fiber compressor as pump sources.