EIA: The Effect of Hydrogen on Optical Damage in Ti DiffusedLiNbO3 Waveguides

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This work is funded as an Engineering Initiation Award (EIA). The presence of hydrogen in lithium niobate crystals has been found to make Ti-diffused waveguides less susceptible to photorefractive optical damage. This project is aimed at understanding how the hydrogen additions lower damage. The work will proceed in five stages: (1) Annealing at high temperature in a controlled gas environment will be used for equilibration (oxygen, lithium, and water activities will be controlled simultaneously); (2) FTIR, Raman, and optical spectroscopies will be used to analyze the equilibrated crystals; (3) the bulk photorefractive effect will be measured by writing holographic diffraction gratings; (4) planar waveguides will be made by in-diffusion of titanium; and (5) optical damage in the waveguides will be measured. The results of each of these steps will be correlated to understand what hydrogen defects are present and what their effects are. A better understanding of hydrogen in lithium niobate will allow fabrication of waveguides with longer life and higher power transmission capabilities. This proposal describes work which will further characterize the photorefractive effect in lithium niobate. The understanding obtained in the proposed study should allow the fabrication of improved optical devices. The major thrusts of this study will be to identify hydrogen related defects which are likely to be present in lithium niobate, and to assess their positive or negative effects on the photorefractive effect. The identifications will be made by studying crystals which have been equilibrated in carefully controlled environments.