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. 2019 Sep 27;19(19):4210.
doi: 10.3390/s19194210.

Sensitivity Enhancement of a Concave Shaped Optical Fiber Refractive Index Sensor Covered with Multiple Au Nanowires

A K Pathak  1   2 , B M A Rahman  3 , V K Singh  4 , S Kumari  5
Affiliations
Free PMC article

Sensitivity Enhancement of a Concave Shaped Optical Fiber Refractive Index Sensor Covered with Multiple Au Nanowires

A K Pathak et al. Sensors (Basel). .
Free PMC article

Abstract

In the present paper, a new kind of concave shaped refractive index sensor (CSRIS) exploiting localized surface plasmon resonance (LSPR) is proposed and numerically optimized. The LSPR effect between polaritons and the core guided mode of designed CSRIS is used to enhance the sensing performance. The sensor is characterized for two types of sensing structures coated with gold (Au) film and Au nanowires (AuNWs), respectively. The influence of structural parameters such as the distance (D) of the concave shaped channel (CSC) from the core, the diameter of the nanowire (dn) and the size (s) of the CSC are investigated here. In comparison to Au film, the AuNWs are shown to significantly enhance the sensitivity and the performance of the designed sensor. An enhanced sensitivity of 4471 nm/RIU (refractive index unit) is obtained with AuNWs, for a wide range of analytes refractive index (na) varying between 1.33 to 1.38. However, for conventional Au film; the sensitivity of 808.57 nm/RIU is obtained for the same range of analytes.

Keywords: microfluidic channel; nanowires; refractive index; sensitivity; surface plasmon resonance.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic diagram of the designed concave shaped refractive index sensor (CSRIS) (a) cross section of designed sensor, (b) and (c) are the zoomed in and further magnified diagram of gold nanowires (AuNWs) covered concave shaped channel (CSC), respectively.
Figure 2
Figure 2
Dispersion curve for both Au thin film/NWs.
Figure 3
Figure 3
(a) and (d) show electric field distribution Ey near film and NWs, respectively, (b) and (e) show the enlarged view; (c) and (f) show the Ey field variation along the y-axis, for Au film and NWs, respectively.
Figure 4
Figure 4
Variation in confinement loss spectra at various separations between CSC and the core for (a) AuNWs and (b) Au film.
Figure 5
Figure 5
Variation in loss spectra with the wavelength for at different dn and tAu (a) AuNWs and (b) Au film, respectively.
Figure 6
Figure 6
Loss spectra with the variation of channel size for (a) AuNWs and (b) Au film.
Figure 7
Figure 7
(a) Loss spectra and (b) amplitude sensitivity due to the changes of na for AuNWs filled CSRIS.
Figure 8
Figure 8
Sensitivity plot of the designed sensors for both AuNWs and Au film.
Figure 9
Figure 9
(a) Loss spectra and (b) amplitude sensitivity, with ±2% variation in separation of CSC from core.
Figure 10
Figure 10
(a) Loss spectra and (b) amplitude sensitivity, with ±2% variation in dn of AuNWs.
Figure 11
Figure 11
(a) Loss spectra and (b) amplitude sensitivity, with ±2% tolerance in CSC size (s).
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