Sensitivity Comparison of Refractive Index Transducer Optical Fiber Based on Surface Plasmon Resonance Using Ag, Cu, and Bimetallic Ag–Cu Layer

Abstract

A single-mode optical fiber sensor uses surface plasmon resonance (SPR) with a bimetallic silver–copper (Ag–Cu) coating compared to a single layer of Ag and Cu itself. Bimetallic Ag–Cu sensors are constructed by simple fabrication on a side-polished optical fiber, followed by an electron beam evaporation of Ag and Cu films. For this investigation, the thickness of the single Ag layer was set to 30 nm and the single Cu layer was set to 30 nm; whereas for the bimetallic combined Ag–Cu layer the thickness of Ag was 7 nm and Cu 23 nm. The sensor performance was analyzed and compared experimentally and numerically using the COMSOL Multiphysics. A white light source was used with a broad optical bandwidth to provide a range of wavelengths to the optical fiber. The characteristics of the thin layers of Ag, Cu, and Ag–Cu as alcohol sensors were evaluated. We found that Cu was the most sensitive metallic layer compared to the Ag and the bimetallic Ag–Cu layers. For a 100% alcohol concentration, Cu showed a sensitivity of 425 nm/RIU followed by the bimetallic Ag–Cu layer with 108.33 nm/RIU, whereas the Ag layer was not detected. Interestingly, sensitivity reached saturation beyond the 20 nm thick layer of Ag. This shows that the Cu and the bimetallic Ag–Cu layers are suitable for an alcohol-based optical sensor.

Robust ZTO-reinforced Ag nanowire hybrid transparent conductive thin films with absorption-enhanced electromagnetic interference shielding property

“…Transmittance dips were observed at 375 nm for all the AgNW films (figures S2) irrespective of ratio, which is the optical signature of AgNWs caused by the surface plasmon resonance (SPR) [34], and for ZSZ hybrid thin films it was observed between 410-420 nm (figure 6). The transmittance dips has shifted significantly towards the visible region in ZSZ films; this is ascribed to the SPR wavelength shift induced by the change in refractive index by ZTO encapsulation [35][36][37]. The ZSZ films showed uniform transmittance in the visible region which extends up to to the near-infrared region (750-1100 nm) (listed in table 2).…”

Advances in Plasmonic Sensing at the NIR—A Review

“…Efforts to enhance the Cu properties in plasmonics have been achieved mainly by employing bimetallic schemes. Zakaria et al [ 122 ] simulated and experimentally developed a bimetallic Ag-Cu thin film, and further deposited on a side-polished optical fiber. It was tested the RI sensitivity, showing a typical value of 108 nm/RIU for the bimetallic film, and for Cu only, a sensitivity of 425 nm/RIU.…”

“…To date it, in the literature, an immense use of Au NS and their property dependence upon geometrical and volume effects on the resonance band can be found, and since such geometries are now widely available, new compositions are being used, such as bimetallic NS, with a metal or dielectric core and metallic shell [ 105 , 118 , 119 , 120 , 121 , 122 ]. Although various bimetallic systems have been studied, with AuPd, CuNi and others, Au and Ag combinations are particularly common in the VIS-NIR range [ 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 ].…”

An Improved Seeker Optimization Algorithm for Phase Sensitivity Enhancement of a Franckeite- and WS2-Based SPR Biosensor for Waterborne Bacteria Detection

“…Surface plasmon resonance (SPR) biosensors utilize plasmon waves to measure alterations in the refractive index occurring on the sensing surface [ 1 ]. Numerous benefits of the SPR biosensor include its low cost, straightforward design, excellent sensitivity, label-free detection, and real-time characteristics [ 2 , 3 , 4 ]. Its potential applications are extensive and include biological detection, food safety, environmental pollution detection, and other domains [ 5 , 6 , 7 ].…”