Compact Electric-field Sensor Based on Lithium-niobate Waveguide Grating

Project: Research

View graph of relations


Instantaneous, strong electromagnetic pulses (EMPs) can appear in extreme weather conditions, nuclear detonation, and electricity supply. Failure in detecting EMPs generated by high-energy facilities, such as nuclear plants and high-voltage power grids, could cause serious disasters in electricity, communication, transportation, and military systems. Conventional electric-field sensors based on metallic structures and antenna probes may disturb the electric field to be measured and give inaccurate results. To avoid mutual electromagnetic interferences, optical electric-field sensors have long been investigated. In particular, compact lithium-niobate (LiNbO3) electric-field sensors based on the large electro-optic effect of LiNbO3 can provide non-invasive, real-time, and long-term measurements with high sensitivities, large dynamic ranges, and broadband frequency responses and stand out as the most promising optical electric-field sensors. Existing LiNbO3 electric-field sensors are mostly configured as waveguide interferometers. The periodic transmission spectra of waveguide interferometers, however, present difficulties in the identification of the operation condition and the multiplexing of multiple sensors. In this project, the PI proposes a new LiNbO3 electric-field sensor configuration to overcome the limitations of the conventional LiNbO3 sensors. The proposed sensor consists of a LiNbO3 waveguide that supports two guided modes, where properly designed periodic shielding electrodes are placed on the waveguide surface. When the waveguide is exposed to an electric field, a periodic modulation in the refractive index of the waveguide, namely a long-period grating, is formed in the waveguide, which enables the fundamental mode of the waveguide to couple to the higher-order mode at a specific resonance wavelength. The transmission of the fundamental mode at the resonance wavelength thus serves as a measure of the external electric field. This sensor configuration removes the ambiguity in the identification of the operation wavelength and allows multiplexing of sensors designed for different wavelengths. In this project, the principle of the proposed sensor will be investigated theoretically and experimentally, and the parameters of the sensor will be optimized for different applications. Centimeter-long prototype sensor chips will be fabricated and fully tested. The PI has over 30 years research experience in the field of waveguide devices, including LiNbO3 devices. He is a pioneer in the development of waveguide devices based on long-period grating structures and CityU possesses all the necessary facilities for the fabrication of the proposed sensors. The PI has all the capacity to complete this project. The outcome of the project should benefit all industries that require reliable measurement of electric fields.  


Project number9043333
Grant typeGRF
Effective start/end date1/01/23 → …