Metamaterial as perfect absorber for high sensitivity refractive index based biosensing applications at infrared frequencies

Abstract

In this paper, we introduce a novel design of a metamaterial unit cell absorber, which is based on a metal/insulator/metal sandwich structure. The design is subjected to comprehensive finite element method (FEM) computational analysis to ensure accurate and reliable results. The proposed metamaterial sandwich structure demonstrates exceptional absorption performance, achieving a nearly perfect absorption rate of 99.996% at the resonance infrared frequency of 39.8 THz. To provide a detailed theoretical explanation of nearly perfect absorption, we employ the effective medium theory, impedance matching, and field distribution analysis. Additionally, we have optimized the structural parameters of the sensor to maximize its absorption peak. This includes optimizing the thickness of the gold (Au) layer (from 0.03 to 0.28 μm), the distance between the L shape corners (from 0.60 to 0.90 μm), and the thickness of SiC dielectric spacer (from 0.20 to 0.45 μm). Furthermore, we showcase the remarkable sensitivity of the proposed metamaterial unit cell in detecting subtle changes in the refractive index through the implementation of a sensing medium setup in our model. Remarkably, we achieve a frequency shift sensitivity of 3.74 THz/RIU, along with a quality factor (Q-factor) of 10.33, for a wide range of refractive indices (1.0 - 2.0). Moreover, for cancer detection, we attain a sensitivity of 3.5 THz/RIU. These findings highlight the exceptional performance of our approach in accurately detecting changes in refractive index, making it a promising candidate for various sensing applications. The novelty of our work lies in the design of a metamaterial unit cell structure. This configuration exhibits several noteworthy features, including wide incident angle (θ) coverage up to 60o, polarization insensitivity, exceptional frequency shift sensitivity, high absorption peaks across a wide range of refractive indices, and the ability to distinguish cancer cells from healthy ones.

Advancements and Perspectives in Optical Biosensors

“…The progression of material science and the accuracy of numerical analysis play vital roles in the recent development of optical biosensors. Simulation software such as COMSOL Multiphysics, , FDTD, , and CST provides a closer look and helps to analyze experimental results for various geometrical and material parameters optimizations of biosensing platforms. Additionally, the combination of microfluidics , and, importantly, the most recent developments in flexible and stretchable optical sensors have opened pathways to new functionalities and have become the most useable POC devices.…”

“…Binding interactions involving the target analyte in the medium change the refractive index, which can be easily detected by measuring changes in the resonance conditions. Commercial numerical software packages such as CST Studio Suite 132 and COMSOL Multiphysics 36 are mainly used to observe electric and magnetic field augmentation during resonance conditions.…”

“…In optical biosensing, some essential sensor parameters are sensitivity, specificity, signal-to-noise ratio, detection limit, etc. The sensitivity is calculated based on the change of the resonance condition, such as for the wavelength-based interrogation method; the wavelength sensitivity is defined as the ratio of the resonance wavelength shifts due to the change in the concentration of bioassays . Similarly, for the angular interrogation method, the sensitivity is calculated as the ratio of resonance angle changes with the concentration change in the bioassays .…”

“…The sensitivity is calculated based on the change of the resonance condition, such as for the wavelength-based interrogation method; the wavelength sensitivity is defined as the ratio of the resonance wavelength shifts due to the change in the concentration of bioassays. 36 Similarly, for the angular interrogation method, the sensitivity is calculated as the ratio of resonance angle changes with the concentration change in the bioassays. 28 The detection limit is the minimum amount of concentration required to detect a change in the resonance condition.…”

A highly tunable biosensor in graphene-vanadium dioxide hyperbolic metamaterial based on surface plasmon resonance

“…Utilizing the GH shift as a probe for this biosensor, we investigated the application of this biosensing structure in discriminating cancer cells from normal cells. The GHMM structure used in our proposed biosensor is structurally simpler and less costly compared to metamaterials made by photolithographic processes [39,40], can be directly realized by physical deposition, and has a wider range of performance modulation capabilities in the frequency range.…”