Suppression of Crosstalk Drift in Ti: LiNbO₃ Waveguide Switches

We report on dc drift characteristics with short relaxation times (typically 20–30 s) of LiNb0₃-based electrooptic switches for use at the wavelength of 1.3 μm. We evaluated the switch elements without oxide buffer layers to focus on the substrate. Sputter-etching of more than 20 nm of the substrate surface after waveguide fabrication results in a remarkable suppression of the drift: drift-induced crosstalk of below -25 dB has been achieved. The sputtering process also reduces the range of scatter of voltage drift among four switches fabricated on a single substrate. With data on the capacitance and resistance between a pair of electrodes, the above effects are attributed to the removal of the surface layer by sputtering.