Time resolved measurements of gratings photo-induced by femtosecond pulses in a lead doped glass

Abstract

We report on the formation of gratings photo-induced by femtosecond laser pulses in SF59 glass. Depending on the number of pulses used to excite the sample and the pump power density, transient or permanent gratings are induced. We demonstrate that the grating formation is not instantaneous and is produced by laser-induced defects. This results in a change of both the real and imaginary part of the index of refraction. A simple setup that records the temporal evolution of both parameters during the laser excitation is also presented. It makes it possible to evaluate the weight of both contributions to the grating diffraction efficiency.

Study of femtosecond laser-induced grating in lead silicate glasses

“…The grating was directly written onto the SF glasses by imaging a master grating, which is illuminated by femtosecond laser pulses (1mJ, ~50fs, 1KHz, ~800nm) [2]. The formation of the grating was shown to result from defects photo-induced by the two photon-absorption of the femtosecond laser pulses [1,2]. Theses defects induce a change of the real (Δn r ) and imaginary (Δn i ) part of refractive index of the glass.…”

“…The grating reflectivity was shown to depend on the pump power density and on the number of exciting pulses [1]. The grating was directly written onto the SF glasses by imaging a master grating, which is illuminated by femtosecond laser pulses (1mJ, ~50fs, 1KHz, ~800nm) [2].…”