Proton-exchanged LiNbO3 waveguides: the effects ofpost-exchange annealing and buffered melts as determined by infraredspectroscopy, optical waveguide measurements, and hydrogen isotopicexchange reactions |
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Authors: | Loni A Hay G De La Rue RM Winfield JM |
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Affiliation: | Glasgow Univ.; |
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Abstract: | Infrared spectroscopy in the OH stretching region has been used to determine the extent of proton exchange in x- and z-cut lithium niobate as a function of temperature and time. The behavior observed is consistent with the occurrence of a diffusion-limited process within LiNbO3. Apparent activation energies for the process determined from infrared spectroscopic measurements are consistent with the existence of a minimum exchange temperature and show that a relationship exists between waveguide depth and absorption band area. The measurements are also shown that hydrogen-bonded OH is substantially removed by annealing and that the extent of its formation is reduced by using buffered (lithium benzoate/benzoic acid) melts. It is suggested that hydrogen-bonded OH groups are responsible for many of the problems associated with proton-exchanged waveguides. Therefore, implementation of either annealing or buffered melts as part of the fabrication process is required to realize good-quality proton-exchanged waveguides |
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