Ultrasensitive biosensor using a Fano resonant asymmetric all-dielectric metasurface

Abstract

Fano resonance is a universal phenomenon that has been widely exploited to achieve spectrally sharp resonances for a variety of applications. Recently, all dielectric metasurface design composed of two silicon resonators, nanodisk and nanobar, exhibits an induced transparency window with ultrahigh quality factor in polarization direction along the nanobar long axis relying on the intriguing physics of Fano resonance. However, the design demonstrates a dispersive behavior within a short spectral range, a phenomenon that hinders its practical usage as a Biosensor due to the lack of the spectral selectivity. In this work, we report the tunable design along the range of wavelengths from 1.2 𝜇m to 1.75 𝜇m through changing the radius of the nanodisk from 200nm to 350nm. Although the design demonstrates a spectral red shift of the reflection with increasing the nanodisk radius, the reflectance behavior is inconsistent indicating the formation of transparency windows in most cases. Worthwhile, the structure design of radius (r=300nm) enables attaining a single sharp Fano resonance addressing the aforementioned short range dispersion obstacle. Meanwhile, the optimized design of radius of (r=300nm) provides a significant quality factor of (~808) and ultrahigh sensitivity of (275nm/RIU) with a figure-ofmerit of (148) at the operating wavelength of (𝜆=1.583𝜇m). The proposed design demonstrates a tremendous impact in refractometric biosensing applications due to its high performance and the ease of fabrication.

Silicon based Double Fano resonances photonic integrated gas sensor

“…On the other hand, structures based on all-dielectric high index material such as the periodic "Lucky knot" shaped nanostructure 40 , split bar resonator 41 , and periodic unit cells of coupled rectangular bar and ring resonators 42 , coupled nano-bar with nanodisk 43 , coupled nano-ellipse with nano-bar 44 , are employed for sensing applications for different materials. All-dielectric structures show enhanced quality factors reaching up to 980 in some cases 41 , however with less sensitivity than their plasmonic counterparts.…”

Recent advances in the metamaterial and metasurface-based biosensor in the gigahertz, terahertz, and optical frequency domains

“…At the working wavelength of ( λ = 1.583 μ m), the structure's sensitivity was (275nm/RIU), resulting in a figure-of-merit (FOM) of (148). Because of its excellent performance and simplicity of manufacture, the suggested design shows great promise for use in refractometric biosensing applications [ 183 ]. In addition, Chen et al presented an all-dielectric metastructure shown in Fig.…”

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Fig. 6 Top (a–b) Schematic diagram of the Fano resonant based all dielectric metasurface design [ 183 ]. Bottom (a–b) Schematic representation of a single cycle of the intended meta-structure, which consists of four silicon blocks shaped like sectors and a cross rod positioned on a silica substrate [184] (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

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