Robertson, E.E., Eason, R.W., Kaczmarek, M., Chandler, P.J. and Huang, X.
Two-wave mixing in photorefractive SBN planar waveguides
At 12th UK National Quantum Electronics Conference (QE12), United Kingdom.
04 - 08 Sep 1995.
Planar waveguides have been fabricated in SBN:61 and SBN:75 by ion-beam implantation. The implantation was carried out using 2.0MeV H+ ions with doses ranging from 2x10 for the TE mode. These losses are significantly lower than those observed for planar waveguides fabricated previously using sulphur diffusion . Two beam coupling experiments were then carried out on the SBN waveguide where it was observed that the gain direction was the same as that of the bulk crystal. Previously, in both BaTiO3  and KNbO3  planar waveguides fabricated in the same manner, the gain direction for two beam coupling had been shown to reverse. This phenomenon may be due to the ion beam implantation process reducing the waveguide layer and subsequently changing the ratio of impurity atom oxidation states - in the case of BaTiO3, the ratio of Fe2+:Fe3+. It is thought that the predominant photoexcited charge carrier in both BaTiO3 and KNbO3 is changed from the hole to the electron whereas in SBN, the electron remains the predominant carrier even after the implantation process. Modelling of these effects has been undertaken, giving an explanation of why gain reversal should occur in certain photorefractive planar waveguides fabricated by ion-beam implantation.
This paper will discuss the gain and response time of the SBN waveguide in comparison to the bulk and the theoretical predictions of the effects of ion-beam implantation on photorefractive materials
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