Characteristics of the oscillatory spectrum due to only induced-phase modulation in an argon-filled hollow waveguide accompanied with intense self-phase modulation

We experimentally observed the periodic oscillatory structure in the second -harmonic spectrum when we simultaneously propagated intense fundamental an d second-harmonic pulses from a Ti:sapphire laser-amplifier system in an ar gon-filled capillary fiber. The periodic oscillatory structure in the secon d-harmonic spectrum is only due to the induced-phase modulation (IPM) which , in general, is hidden because of strong self-phase modulation. It is foun d that this structure can be well explained by the interference of the elec tric field components in the second-harmonic pulse. These electric field co mponents are generated based on IPM by the fundamental pulse, The theoretic al analysis of the nonlinear pulse propagation agrees well with experimenta l results. In addition, the measured dependence of the modulated spectral b ehavior on the delay time, including the spectral feature, the oscillatory period and the range of the delay time between two pulses, indicates the ex cellent agreement with the numerical analysis which includes the medium and waveguide dispersion and the steepening effect. (C) 2001 Elsevier Science BN. All rights reserved.