Fano-resonant electric field sensor based on the thin film lithium niobate micro-ring with enhanced sensitivity

Electric field sensing is vital for applications ranging from telecommunications to biomedical diagnostics, where high sensitivity and compact form factors are increasingly demanded. Traditional photonic integrated electric field sensors, despite leveraging electro-optic effects, often enhance sensitivity by enlarging interaction regions or complex optoelectronic circuits, compromising device scalability and footprint. Here, we demonstrate an electric field sensor on a lithium niobate on insulator (LNOI) platform that enhances sensitivity by leveraging Fano resonance. By incorporating a hole into a conventional micro-ring resonator (MRR), we engineered sharp Fano lineshapes exhibiting a spectral slope rate reaching 1721 dB/nm, significantly surpassing the 472 dB/nm slope of unmodified MRRs. This spectral enhancement delivers a sensitivity of 0.55 V/m/Hz^1/2 compared to 1.17 V/m/Hz^1/2 of unmodified MRR, advancing the performance of LNOI-based sensors without increasing footprint. This work marks the first integration of Fano resonance on the LNOI platform for electric field sensing, harnessing the material's strong electro-optic properties alongside innovative spectral engineering. These findings establish a promising foundation for the development of miniaturized, high-performance photonic electric field sensors across a wide range of fields.