Conical emission of a femtosecond laser pulse focused by an axicon into a K 108 glass

The supercontinuum conical emission of a 50-fs laser pulse focused into a K108 glass is studied experimentally and numerically. It is found that, as the pulse energy was increased from 2 to 30 mu J, the continuous picture of conical emission decomposed into speckles upon focusing with a lens and split into narrow rings upon focusing with an axicon.