Depression of the surface index of TiLiNbO3 channel waveguides by secondary diffusion of MgO forms a buffer layer that optically isolates the guided modes from attenuation caused by electrodes placed over the guides. For x-cut, z-propagating mode-conversion devices, we find high stability to optical drift when a dc voltage as high as 60 V is applied to electrodes (typical gap of 5 μm) to establish bias operating points. Photoconductivity is found to limit the long-term stability. Devices operating at 0.633-μm wavelength generally suffer significant drift in their mode-conversion efficiency when 100 μW or more of throughput power is present and a bias of 14 V is used. 10-μW throughput at the same wavelength is found to be stable over an 8-h period. At 0.8-μm wavelength, bias voltages as high as 60 V may be used for stable operation even at 100-μW optical throughput.
© 1987 Optical Society of AmericaFull Article | PDF Article
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