Photorefractive effect in proton-implanted Fe-doped KNbO_3 waveguides at telecommunication wavelengths

We report on photorefractive two-beam coupling in proton-implanted Fe-doped KNbO3 waveguides at wavelengths from 632.8 to 1550 nm. Exponential gain coefficients of 11 and 0.9 cm-1 were measured at wavelengths of 632.8 nm and 1550 nm, respectively. Photorefractive response times as low as 120 µs are reported at 632.8 nm for a pump power of 4 mW. It is shown that proton irradiation increases the effective trap density, decreases the response time, and extends the photorefractive sensitivity of Fe-doped KNbO3 crystals toward near-infrared wavelengths.