Nanograting formation on the surface of silica glass by scanning focused femtosecond laser pulses.

We have investigated the formation of nanogratings induced by femtosecond laser pulses on the surface of silica glass blocks. The nanograting period ranges between 170 and 340 nm, depending on the pulse-to-pulse spacing, whereas for a given spacing the period remains constant upon changing the laser pulse energy. Intensity clamping is proposed as the mechanism that is responsible for such independence of the grating period from pulse energy.