Photorefractive α -Phase Proton-Exchanged LiNbO₃ Waveguides Prepared on Iron Doped Substrates

Abstract

In order to enhance the photorefractive effect of α -phase proton-exchanged LiNbO ₃ waveguides, they have been prepared in Fe-doped LiNbO ₃ substrates. The reduction state of the impurity, crucial in photorefractive performance, has been investigated. It has been found that this parameter is very sensitive to the duration of the proton exchange treatment. This result has been corroborated in undoped waveguides. Holographic gratings have been recorded in the waveguide layer, obtaining refractive index changes greater than those found in undoped waveguides and diffraction efficiencies of about 100%. The dark conductivity, measured through the dark decays of the gratings, is lower but comparable with that measured in undoped waveguides.

Keywords:

• Photorefractive effect
• LiNbO₃
• optical waveguides

Acknowledgments

This work was supported by the Ministerio de Educación y Ciencia under grants MEC/MAT2005-06359-C03-01. J. Carnicero acknowledges the financial support of the MEC through his FPU fellowship. We also want to thank Professor J. M. Cabrera for useful discussions and comments.