Intense self-compressed, self-phase-stabilized few-cycle pulses at 2 μm from an optical filament

We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by using self-phase stabilized 330 mu J 55 fs pulses at 2 am produced via difference-frequency generation in a Ti:sapphire-pumped optical parametric amplifier. The ultrabroadband 2 mu m carrier-wavelength output is self-compressed below 3 optical cycles and has a 270 mu J pulse energy. The self-locked phase offset of the 2 mu m difference-frequency field is preserved after filamentation. This is to our knowledge the first experimental realization of pulse compression in optical filaments at mid-IR wavelengths (lambda > 0.8 mu m). (c) 2007 Optical Society of America.