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. 2022 Sep 28;12(19):3396.
doi: 10.3390/nano12193396.

A Nanoscale Sensor Based on a Toroidal Cavity with a Built-In Elliptical Ring Structure for Temperature Sensing Application

Feng Liu  1   2   3 , Shubin Yan  2   3 , Lifang Shen  2 , Pengwei Liu  1   2   3 , Lili Chen  2 , Xiaoyu Zhang  1   2   3 , Guang Liu  2 , Jilai Liu  2 , Tingsong Li  1   2   3 , Yifeng Ren  1
Affiliations

A Nanoscale Sensor Based on a Toroidal Cavity with a Built-In Elliptical Ring Structure for Temperature Sensing Application

Feng Liu et al. Nanomaterials (Basel). .

Abstract

In this article, a refractive index sensor based on Fano resonance, which is generated by the coupling of a metal-insulator-metal (MIM) waveguide structure and a toroidal cavity with a built-in elliptical ring (TCER) structure, is presented. The finite element method (FEM) was employed to analyze the propagation characteristics of the integral structure. The effects of refractive index and different geometric parameters of the structure on the sensing characteristics were evaluated. The maximum sensitivity was 2220 nm/RIU with a figure of merit (FOM) of 58.7, which is the best performance level that the designed structure could achieve. Moreover, due to its high sensitivity and simple structure, the refractive index sensor can be applied in the field of temperature detection, and its sensitivity is calculated to be 1.187 nm/℃.

Keywords: Fano resonance; MIM; refractive index sensor; temperature sensing.

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Conflict of interest statement

The authors declare no conflict of the interest.

Figures

Figure 1
Figure 1
2D schematic of an MIM waveguide and a toroidal cavity with a built-in elliptical ring (TCER).
Figure 2
Figure 2
Transmission spectra of the rectangle stub (black line), the TCER structure (red line), and integral structure (blue line).
Figure 3
Figure 3
Normalized magnetic field distributions at λ = 1891 nm of (a) the TCER structure; (b) the entire system.
Figure 4
Figure 4
(a) Transmission spectra for diverse refractive indices. (b) Fitting line of dip wavelength change with refractive index variation.
Figure 5
Figure 5
(a) Transmission spectra of the entire structure at various radii R. (b) Fitting line of sensitivity under diverse radii.
Figure 6
Figure 6
(a) Transmission spectra of TCER structure under disparate minor semi-axes of outer ellipses. (b) Fitting line of sensitivity at diverse minor semi-axes.
Figure 7
Figure 7
Transmission spectra at various rectangular baffle heights.
Figure 8
Figure 8
(a) Transmission spectra under different coupling gaps. (b) Changes of FWHM values at different coupling distances. (c) Fitting line of sensitivity at diverse coupling gaps.
Figure 9
Figure 9
(a) Transmission spectra at gradually increasing temperature. (b) Sensitivity fitting line for temperature sensors.
See this image and copyright information in PMC

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