Abstract
The formation of periodically polarized waveguide structures in lithium niobate crystals for nonlinear optical transformations of laser radiation in the telecommunications wavelength range is an important applied problem. One of the options for forming waveguides with low switching fields can be waveguides obtained by soft proton exchange. In this work, using X-ray diffraction analysis, it is shown that anomalously low polarization switching thresholds occur in layers with so-called intermediate κ-phases when varying the time of soft proton exchange, and when varying the concentration of lithium benzoate, a transition from the metastable β-phase to the intermediate κ-phase is revealed. The results obtained support the hypothesis that the proton concentration gradient leads to a decrease in the threshold field for polarization switching. However, high-concentration metastable and intermediate crystalline phases lead to an increase in optical losses and temperature instability of waveguides.
Published Version
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