Reflection and propagation of laser pulse with a few cycles in medium with time-dependent dielectric permittivity

Abstract

On the base of computer simulation, we investigated a propagation of femtosecond laser pulse in a linear medium with time-dependent dielectric permittivity. We showed that in dependence on the relation between carrier frequency of wave package and the modulation frequency of a medium the various phenomena take place: frequency conversion, instability. We analyze two cases: dielectric permittivity modulation is unlimited during time or the modulation is limited during time. We show that for incident laser pulse with a few cycles the influence of its absolute phase is strong. For such incident pulse, a high enrichment of a spectrum of the laser pulse, propagated in a medium with time-dependent dielectric permittivity, takes place. This enrichment may be similar to the spectrum enrichment if a perturbation of the dielectric permittivity occurs unlimited during time. We believe that considering scheme of laser pulse interaction with medium can be used in data processing by optical methods, for example.