Temperature characteristics of a Y-cut Z-propagation LiNbO3 light modulator for application to polarimeters

The temperature characteristics of a Y-cut Z-propagation LiNbO₃ crystal light modulator, with manufacturing errors, in the absence and presence of an electric field have been investigated by analyses and experiments. According to our analyses, when the Z-axis of the LiNbO₃ crystal is at an angle of 0.22° with respect to the normal of the input surface of the crystal, we found the theoretical fluctuation of the normalized output-light intensity with temperature to be less than 7:75 × 10⁻⁶/°C. This magnitude is less than 1% of the theoretical intensity fluctuation of a conventional temperature-compensation LiNbO₃ light modulator. The measured temperature characteristics of a prototype of this modulator were 2 × 10⁻⁴/°C in the absence of an electric field (OFF state) and 2:8 × 10⁻⁴/°C in the presence of an external field (ON state). During a running test of longer than 8 hours at room temperature, the intensity fluctuation of this prototype was 0.01% in the OFF state, and 0.07% in the ON state.