Optical Waveguide Electric Field Sensor Based on Dual Parallel Mach-Zehnder Interferometer

Integrated optical waveguide sensor has characteristics of good insulation, broadband response and small size. A LiNbO
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(LN) integrated optical waveguide sensor based on a dual parallel asymmetric Mach-Zehnder interferometer (DAMZI) and segmented electrode is designed, fabricated and experimentally demonstrated. By using the DAMZI with segmented electrode fabricated between the two straight waveguide arms, a push-pull modulation is generated, yielding a pair of differential signals are formed at the two outputs of the sensor. Thus based on the differential effect of the balanced photo detection (PD) at the receiving end, the noise is suppressed while the signal is enhanced. The noise floor, minimum detectable electric field, and input/output characteristics of the sensor are measured and compared with those of the sensor with single PD. Experiment results demonstrate that in comparison to the sensor with single PD, the noise floor of the sensor with balanced PD is reduced by about 6 dB while the minimum detectable electric field is reduced by about 18 dB. Besides, in the time domain, the minimum detectable electric field and dynamic range of the sensor are 12.5 V/m and 47 dB respectively. The frequency response variation is within ±1 dB from 9 kHz to 340 MHz, and the temperature stability variation is less than ±0.3 dB with the ambient temperature changed from 18 °C to 28 °C within 19 hours. All these results demonstrate that the sensor has powerful potential capability to be used for measuring the weaker electric field in the electromagnetic compatibility (EMC) area.