Far-field spectral characterization of conical emission and filamentation in Kerr media

By use of an imaging spectrometer we map the far-field (theta-lambda) spectra of 200-fs optical pulses that have undergone beam collapse and filamentation in a Kerr medium. By studying the evolution of the spectra with increasing input power and by using a model based on an asymptotic linear superposition of stationary wave modes (rather than the exact instantaneous solution), we are able to trace a consistent model of optical beam collapse highlighting the interplay between conical emission, multiple pulse splitting, and other effects such as spatial chirp.