Supercontinuum sources in a high-power femtosecond laserpulse propagating in liquids and gases

The mechanism of supercontinuum generation and the spatial distribution of its sources during the propagation of a high-power femtosecond laser pulse in liquids and gases are studied. The numerical simulation shows that the supercontinuum is generated due to self-phase modulation of the laser pulse in space and time in the presence of nonlinearity and wave effects. Supercontinuum sources are found to be located mainly in the ring structure of the laser pulse at the intensity minima. It is established that the efficiency of generation of the short-wavelength part of the supercontinuum during the propagation of the focused laser beam depends on the initial phase modulation and achieves a maximum when the compression length slightly exceeds the length of nonlinear focusing.