Highly sensitive and miniaturized sensors are highly desirable for real-time analyte/sample detection. In this Letter, we propose a highly sensitive plasmonic sensing scheme with the miniaturized photonic crystal fiber (PCF) attributes. A large cavity is introduced in the first ring of the PCFs for the efficient field excitation of the surface plasmon polariton mode and proficient infiltration of the sensing elements. Due to the irregular air-hole diameter in the first ring, the cavity exhibits the birefringence behavior which enhances the sensing performance. The novel plasmonic material gold has been used considering the chemical stability in an aqueous environment. The guiding properties and the effects of the sensing performance with different parameters have been investigated by the finite element method, and the proposed PCFs have been fabricated using the stack-and-draw fiber drawing method. The proposed sensor performance was investigated based on the wavelength and amplitude sensing techniques and shows the maximum sensitivities of 11,000 nm/RIU and 1,420 RIU, respectively. It also shows the maximum sensor resolutions of 9.1×10 and 7×10 RIU for the wavelength and amplitude sensing schemes, respectively, and the maximum figure of merits of 407. Furthermore, the proposed sensor is able to detect the analyte refractive indices in the range of 1.33-1.42; as a result, it will find the possible applications in the medical diagnostics, biomolecules, organic chemical, and chemical analyte detection.
Highly sensitive mode-multiplex miniaturized sensors enable the detection and quantification of multiple biomolecules simultaneously through their real-time interactions. Here, we demonstrate a grapefruit photonic crystal fiber (PCF)-based mode-multiplex surface plasmon resonance (SPR) sensor that detects multiple analytes simultaneously. Three grapefruit-shaped air-holes are internally coated with plasmonic gold (Au) material, which allows them to act as mode-multiplex channels that detect three unknown analytes. The sensor performance was investigated using the finite element method (FEM), and the optimized fiber structure was fabricated with the standard stack-and-draw method. For the
y
-polarized mode, channels one and three showed the maximum wavelength sensitivities of 2000 and 18,000 nm/RIU (refractive index unit) at the analyte refractive indices of 1.34 and 1.41, respectively. On the other hand, channel two showed the maximum wavelength sensitivity of 3000 nm/RIU at the analyte refractive index (RI) of 1.36 for the
x
-polarized mode. To the best of our knowledge, this is the first demonstration of a mode-multiplex grapefruit PCF-based SPR sensor to simultaneously detect and quantify three different analytes. We anticipate that the proposed sensor will find potential applications in the detection of real-time biomolecular interactions and binding affinity.
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