Generation of intense ultrabroadband optical pulses by induced phase modulation in an argon-filled single-mode hollow waveguide

We experimentally demonstrate the generation of intense ultrabroadband opti cal pulses whose spectrum ranges from 300 to 1000 nm (700-THz bandwidth) wi th a well-behaved spectral phase and 23-mu J pulse energy by a novel, simpl e setup utilizing induced phase modulation (IPM) in an argon-filled single- mode hollow waveguide. Fundamental as well as second-harmonic pulses produc ed by one common femtosecond pulse from a Ti:sapphire laser-amplifier syste m are copropagated in the hollow waveguide. The effect of the delay time be tween the two input pulses on the IPM spectral broadening is clarified and confirmed to agree with the theoretical result. It is found that the compre ssed pulse duration from this pulse is 1.51 fs if its phase is completely c ompensated for. (C) 2000 Optical Society of America. OCIS codes: 060.4370, 060.7140, 320.5520, 320.5540, 320.7140.