Optical characteristics of supercontinuum generation

Experimental evidence is presented that the supercontinuum generated in H2O or D2O is a surface phenomenon whose origin is at the surface of self-trapped filaments. This is done by a comparison of the output patterns produced by spherical and cylindrical focusing lenses as well as comparison of the polarization of the incident and emitted light. The similarity between the rings emitted during the supercontinuum generation, the conical emission generated in alkali metal vapors, and class II Raman radiation in liquids is pointed out. Thus the supercontinuum has optical properties characteristics of Čerenkov-type processes.