The present invention relates to a novel method and system for inscription of periodic patterns inside or on a surface of a substrate using femtosecond pulse lasers. The method comprises the following steps: (a) receiving a plurality of femtosecond laser pulsed beams, each beam having a certain pulse duration, flux, focal spot size, profile and energy at a certain wavelength of operation; (b) controlling at least one of the pulse duration, flux, focal spot size, focal spot shape, profile and energy of the plurality of laser pulsed beams; (c) directing the plurality of laser pulsed beams onto a certain region of a substrate having an optical axis, to thereby selectively induce at least one of local index change, microvoids and stress-modulated region at a point of interaction between each beam and the certain region; (d) controllably displacing the substrate along its optical axis to create the periodic patterns on a first plane of inscription along the optical axis; and (e) creating spaced-apart planes across the substrate having a controlled index profile.
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