Generation of 2.6 fs optical pulses using induced-phase modulation in a gas-filled hollow fiber

We report quasi-one-optical-cycle pulse compression of the ultrabroadband white-light continuum generated using both induced-phase modulation (IPM) and self-phase modulation (SPM) in a 3.0 atom Ar-gas-filled hollow fiber. Fundamental and second harmonic waves of amplified 30 fs Ti:sapphire laser pulses were irradiated into a 37 cm hollow fiber with an inner diameter of 140 mu m. When the two pulses were temporally overlapped in the hollow fiber, the white-light continuum with the wavelength range of 350-1050 nin was generated. The spectral phase of the white-light continuum was measured by a modified spectral interferometry for direct electric-field reconstruction, and quasi-automatic feedback chirp compensation was carried out using a programmable liquid-crystal spatial light modulator placed on the Fourier plane of a 4-f system. As a result, 2.6 fs, 3.6 mu J, 1.3 cycle transform-limited (TL) pulses with a peak power up to 1.4 GW at a 1 kHz repetition rate were generated in the visible to near-infrared region (the over-one-octave bandwidth of 450-975 nm). The fact that the IPM + SPM light was compressed to the TL duration is important toward the generation of a single, intense one-optical-cycle pulse in the visible region. (c) 2007 Optical Society of America.