Abstract
There are two types of metasurfaces, reflect-array and transmit-array,—which are classified on the basis of structural features. In this paper, we design a transmit-array metasurface for y-polarized incidence which is characterized by having a transmission spectrum with a narrow dip (i.e., less than 3 nm). Furthermore, a tunable polarizer is achieved using linear geometric configurations, realizing a transmittivity ratio between x- and y-polarized incidence ranging from 0.031% to 1%. Based on the narrow-band polarization sensitivity of our polarizer, a biosensor was designed to detect an environmental refractive index ranging from 1.30 to 1.39, with a factor of sensitivity S = 192 nm/RIU and figure of merit (FOM) = 64/RIU. In the case of a narrow-band feature and dips in transmission spectrums close to zero, FOM* can have a value as large as 92,333/RIU. This unique feature makes the novel transmit-array metasurface a potential market candidate in the field of biosensors. Moreover, transmit-array metasurfaces with lossless materials offer great convenience by means of detecting either the reflectance spectrum or the transmission spectrum.
Highlights
Metasurfaces consist of periodic unit cells of one subwavelength thickness and allow for arbitrary manipulation of the amplitude, phase, and polarization of incident light [1,2]
We found that the figure of merit (FOM)* value for the thin-layered structure was 15167/RIU, which is related to high biosensing performance
In summary, we have proposed a tunable polarizer for illumination under x- and y-polarized illumination and normal incidence, based on Mie resonances of dielectric materials in the visible regime
Summary
Metasurfaces consist of periodic unit cells of one subwavelength thickness and allow for arbitrary manipulation of the amplitude, phase, and polarization of incident light [1,2]. Using the above narrow-band polarization sensitivity feature, we can design a biosensor with transmit-array-based metasurfaces to detect the refractive index variation of the surrounding environment. Our biosensor has good performance in the narrow-band transmission spectrum and a factor of sensitivity S = 192 nm/RIU when detecting a large range of refractive indexes, n, ranging from 1.3 to 1.39. Benefiting from the distinct narrow-band transmission spectrum in the environment and an extremely low transmittivity of 0.06% in resonant wavelengths with different refractive index, the figure of merit (FOM*)—one practical factor used to evaluate the performance of biosensors, which is concerned about the intensity variation due to the refractive index variation—can have a value as large as 92,333/RIU. We present a new method to design high-performance biosensors by utilizing transmit-metasurfaces with narrow-band polarization dependence
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