Fabrication of reflective volume gratings in pulsed-laser-deposition Ti:sapphire waveguides with UV femtosecond-laser pulses

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 ions were observed, which were completely reversible at temperatures of ∼100°C. 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 Ti3+ and Ti4+ ions and/or transient localized structural re-arrangements