High-sensitivity nanostructure-based sensor using Fano resonance for noninvasive EEG monitoring

•Innovatively introducing a 50 nm wide narrow slit in photonic crystal waveguides to highly concentrate the electric field generated by EEG signals in the resonant cavity.•The experimental results show that this sensor has an ultra-high sensing sensitivity of up to 142.64 nm/V and is able to detect EEG signals of 10 μV size.•Due to the optically coupled nanoscale sensing structure, this sensor has a compact footprint as small as 4.29 mm2.•The proposed sensor can be easily integrated with other photonic devices at the chip level, providing a novel solution for the development of miniature physiological sensors. Noninvasive electroencephalogram signal detection with high sensitivity and a high signal-to-noise ratio has attracted much attention. To achieve high-sensitivity electroencephalogram (EEG) sensing, a photonic crystal side-coupled microcavity nanoscale sensor based on Fano resonance is proposed with nano electro-optic sensing technology as the core support. This configuration comprises a nanobeam resonant cavity, a waveguide, and an electrical slab. The substantial overlap between the optical and electric fields within the resonant cavity is analyzed, and the sensor’s electric field sensing performance is assessed. Due to the optically coupled nanoscale sensing structure that is adopted in the sensor, the device has an ultrahigh voltage sensing sensitivity of up to 142.64 nm/V and a compact footprint as small as 4.29 mm2, enabling real-time sensing of EEG signals of 10 μV and below. These improvements overcome the technical challenges of low precision and large size as are associated with existing optical devices used for medical monitoring.