Ultrafast laser-induced index grating in transparent insulators

We report on new results of third harmonic generation and self-diffraction. These effects are related to the occurrence of a refractive index grating produced in transparent dielectrics, in particular in barium fluoride, under irradiation by femtosecond laser pulses. Because only nonresonant electronic nonlinearities are exploited, all described effects are quasi instantaneous. As a result of the high intensities at weak energy obtainable from femtosecond laser systems these effects are very efficient