Fabrication of reflective volume gratings in pulsed-laser-deposited Tiisapphire waveguides with UV femtosecond laser pulses

摘要

Highly reflective volume Bragg gratings (R ～ 80%) were written in Ti:sapphire planar and channel waveguides fabricated via pulsed-laser deposition (PLD) by exposure to UV (266 nm) femtosecond laser irradiation through suitable phase masks. Large photo-induced refractive index modulations of up to ～1 × 10~(-2) were observed, which were completely reversible at temperatures of ～100℃. The dependence of the refractive index modulation on intensity suggests that the mechanism for grating inscription is an one-photon absorption process. Generation of gratings may result from a charge transfer process between the Ti~(3+) and Ti~(4+) ions and/or transient localized structural re-arrangements.