Single-pulse magneto-optic microscopy: a new tool for studying optically induced magnetization reversals.

We have developed a femtosecond magneto-optical imaging system that allows measurements of permanent magnetic effects that are initiated by a single excitation pulse. The system combines a subpicosecond temporal resolution and a high spatial resolution. We demonstrate the system in an experiment that studies the laser-induced magnetization reversal in ferromagnetic thin films.

Near-field imaging of nonlinear pulse propagation in planar silica waveguides.

A simplified near-field scanning optical microscope is employed to image the propagation of short laser pulses in planar silica waveguides, in the anomalous dispersion regime, under varying conditions of input beam power and width. Our results show a complex evolution of the transverse intensity profiles of the beam when there is a pronounced difference between the input diffraction and dispersion lengths. Numerical simulations confirm that these complex spatial dynamics are intimately related to the temporal and spectral evolution of the pulse.

Strong spatiotemporal localization in a silica nonlinear waveguide array.

We investigate the propagation of short, intense laser pulses in arrays of coupled silica waveguides, in the anomalous dispersion regime. The nonlinearity induces trapping of the pulse in a single waveguide, over a wide range of input parameters. A sharp transition is observed for single waveguide excitation, from strong diffraction at low powers to strong localization at high powers.