Control of the onset of filamentation in condensed media

Propagation of intense, ultrashort laser pulses through condensed media, like crystals of BaF₂ and sapphire, results in the formation of filaments. We demonstrate that the onset of filamentation may be controlled by rotating the plane of polarization of incident light. We directly visualize filamentation in BaF₂ via six-photon-absorption-induced fluorescence and, concomitantly, by probing the spectral and spatial properties of white light that is generated.