BAND-GAP DEPENDENCE OF THE ULTRAFAST WHITE-LIGHT CONTINUUM

We report an investigation of white-light continuum generation during self-focusing in extendedtransparent media using 140-fs Ti:sapphire laser pulses. A band-gap threshold is found above whichthe width of the continuum tends to increase with increasing band gap and below which there is nocontinuum generation. This is, to our knowledge, the first report of a parameter predicting the widthof the continuum in condensed media. Multiphoton excitation of electrons into the conduction band isproposed as the primary mechanism reponsible for the observations. [S0031-9007(98)06156-0]