Ultrasensitive THz sensing with high-Q Fano resonances in metasurfaces

TL;DR

This paper demonstrates the excitation of high-Q Fano resonances in terahertz metasurfaces, enabling ultrasensitive detection of refractive index changes for chemical and biomolecular sensing.

Contribution

It introduces a method to excite high-Q Fano resonances in planar terahertz metamaterials, achieving unprecedented sensitivity levels for label-free sensing.

Findings

Achieved sensitivity of 7.75 x 10^3 nm/RIU with quadrupole resonances.

Achieved sensitivity of 5.7 x 10^4 nm/RIU with Fano resonances.

Enabled detection of minute spectral shifts due to small refractive index changes.

Abstract

High quality factor resonances are extremely promising for designing ultra-sensitive refractive index label-free sensors since it allows intense interaction between electromagnetic waves and the analyte material. Metamaterial and plasmonic sensing has recently attracted a lot of attention due to subwavelength confinement of electromagnetic fields in the resonant structures. However, the excitation of high quality factor resonances in these systems has been a challenge. We excite an order of magnitude higher quality factor resonances in planar terahertz metamaterials that we exploit for ultrasensitive sensing. The low-loss quadrupole and Fano resonances with extremely narrow linewidths enable us to measure the minute spectral shift caused due to the smallest change in the refractive index of the surrounding media. We achieve sensitivity levels of 7.75 x 10^3 nm/ RIU with quadrupole and 5.7 x 10^4 nm/ RIU with the Fano resonances which could be further enhanced by using thinner substrates. These findings would facilitate the design of ultrasensitive real time chemical and biomolecular sensors in the fingerprint region of the terahertz regime.