Periodic femtosecond filamentation in birefringent media

摘要

We report on the experimental observation of periodic modulation of the axial luminescence intensity along the femtosecond filament track in sapphire and crystal quartz. The physical reason for the modulation is a cyclic transformation of the polarization state of the light pulse traveling in birefringent medium, caused by the phase raid between the ordinary and extraordinary rays, and different cross sections of multiphoton absorption for linear and circular polarizations.