Improving thermal stability of LiNbO3 based electro-optical electric field sensor by depositing a TiO2 film

Electro-optic electric field sensors based on LiNbO3 are widely used for the measurement of electric fields or transient voltages. However, the working bias of the sensor is influenced by the temperature due to the thermo-optic effect of LiNbO3. An athermal electrooptic electric field sensor was demonstrated by coating a thin layer of TiO2 film which has a negative thermo-optic coefficient, on the common-path interferometer based sensor to compensate LiNbO3's positive thermo-optic coefficient. Both calculation and experimental studies were conducted. The experimental results reasonably agree well with the calculated values, and the results show the sensor coated with a 640 nm thick TiO2 film has a much smaller temperature dependence of 0.011 degrees/degrees C compared to the initial value of 0.1 degrees/degrees C.