EAGER: Highly sensitive optical biosensing using bound states in the continuum of high-Q all-dielectric metasurfaces

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Biosensors are devices that can recognize and quantitatively detect biological analytes (chemical substances that can be analyzed). Optical biosensors work by converting the concentration of analytes to changes in light-based signals. The importance of such sensitive platforms has been demonstrated once again during the recent pandemic. The goal of this research project is to study the principles of a novel type of optical biosensing platform that can be used as highly sensitive low-cost diagnostic tools for improved personalized and stratified treatment at point of care facilities. The sensor design requires engineering of novel surfaces and special layered mirrors in order to create molecular vibrations that can be exploited to measure the concentration of analytes with unprecedentedly low limits of detection, which can be crucial for precise and early detection of pathogens. The approach does not require complex alignment and stabilization which is promising for low-cost and robust biosensing devices. In the framework of the project, a partnership with a local non-profit organization will provide opportunities for K-12 students to broaden their access to STEM learning and careers through lab tours, career talks, science fair judging and other educational activities. The goal of the research is to study optical bound states in the continuum in all-dielectric metasurfaces and explore their properties for the development of highly sensitive optical biosensors. Currently, refractometric label-free biosensing is typically based on resonant plasmonic and metamaterial systems or more complex microring resonators and waveguide interferometers. Unfortunately, most of these systems are either not very sensitive or rely on complex and costly platforms requiring stabilization and precise alignment. This project will explore the coupling of optical magnetic dipole mode of dielectric nanocavities to Bragg mirrors which lead to the formation of unusually high-quality factor resonances that can be used for optical sensing. Unlike the typical state-of-the-art platforms, this novel approach achieves high quality factor bound states in the continuum not via the breaking of local spatial symmetry but through coupling of the optical modes to their mirror image. The resultant resonances are expected to achieve an order of magnitude improvement in quality factors and limit of detection compared to the existing solutions, paving the way for highly sensitive, scalable, spectrometer-less, low-cost optical biosensors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.