Permanent narrow-band reflection holograms for infrared light recorded in LiNbO3 : Ti : Cu channel waveguides

Permanent refractive-index gratings are generated by thermal fixing of holo grams in photorefractive lithium niobate channel waveguides. The guides are fabricated by successive indiffusion of titanium stripes and thin layers o f copper. After high-temperature recording with green light, refractive-ind ex modulations exceeding Deltan = 8 x 10(-5) for light of the telecommunica tion wavelength 1550 nm appear without the need of any development process of the written holograms. The gratings are stable in the dark and no compen sation mechanism via dark conductivity is observed. Thus this method may be well suited for long-time applications in holography and integrated optics .