Highly Sensitive, Affordable, and Adaptable Refractive Index Sensing with Silicon‐Based Dielectric Metasurfaces

A sensing platform is presented that uses dielectric Huygens source metasurfaces to measure refractive index changes in a microfluidic channel with experimentally measured sensitivity of 323 nm RIU−1, a figure of merit (FOM) of 5.4, and a response of 8.2 (820%) change in transmittance per refractive index unit (T/RIU). Changes in the refractive index of liquids flown through the channel are measured by single‐wavelength transmittance measurement, requiring only a simple light source and photodetector, significantly reducing device expense in comparison to state‐of‐the‐art refractive index sensing technologies. A technoeconomic analysis predicts a device costing ≈$2400 that is capable of detecting refractive index changes of the order of 2*10−8. The metasurfaces utilized are low profile, scalable, and use materials and fabrication processes compatible with CMOS and other technologies making them suitable for device integration. The Huygens metasurface system, characterized by spectrally overlapping electric and magnetic dipole modes, offers a high degree of customizability. Interplay between the two resonances may be controlled via metasurface geometry, leading to tunability of device sensitivity and measurement range. Ultrahigh sensitivity of 350 nm RIU−1 with FOM of 219, corresponding to single‐wavelength sensitivity of 360 RIU−1, is demonstrated computationally through use of antisymmetric resonances of a Huygens metasurface illuminated at small incidence angles. A single‐wavelength dielectric metasurface‐based refractive index sensing platform is demonstrated, showing leading measurement sensitivity at a fraction of the cost of currently available technologies. Tunability of device sensitivity and measurement range are achieved through variation of Huygens metasurface geometry, via interplay between spectrally overlapping electric and magnetic resonant modes. Greatly enhanced sensitivity using antisymmetric resonances is explored.