Ultrasensitive terahertz sensing in all-dielectric asymmetric metasurfaces based on quasi-BIC

The bound state in the continuum (BIC), which supports exceptional resonance in the optical range, has attracted significant attention for its bright applications in sensors and other optical devices. However, it is difficult to cover the analyte's transmission/reflection spectrum since BIC possesses an infinite Q factor. In this work, we proposed a thoughtful all-dielectric columns structure with broken symmetry that supports quasi-BIC to achieve ultrasensitive sensing in the terahertz range. Our metasurfaces consist of a series of periodic unit cells, including two silicon columns with asymmetric cylindrical holes and a SiO2 substrate. Quasi-BIC resonances can be observed by the transmission/reflection spectrum. The quasi-BIC resonances with a narrow frequency width are sensitive to the surrounding media and the sensitivity can achieve 170.58 GHz/RIU. We believe our ultrasensitive sensor with high performance and sensitivity provides an exciting platform for biosensing. (C) 2021 Optical Society of America