Asymmetric spectrum evolution of high power short pulses in AlGaAs waveguides

We measured the self-phase modulation spectra at the output of deep-etched AlGaAs waveguides. The light source was an OPO laser system providing 250 fs long pulses, at wavelengths around 1520 nm, with a peak power as high as 1 kW. FROG measurements of the OPO pulses reveal their asymmetric shape. The multi-peak spectra, observed at the waveguide output, show a dramatic asymmetry and a power shift towards short wavelengths. The interplay between the Kerr non-linearity, dispersion and self-steepening amplifies the initial slight asymmetry of the injected spectrum. Experimental results compare favourably with the numerical solution of the generalized non-linear Schrödinger equation.