This work demonstrates a broadband polarization filter based on copper-filled photonic crystal fiber (CFPCF). The proposed fiber is fabricated using the conventional stack-and-draw method. The polarization filter properties of the proposed CFPCF are investigated numerically by considering the cross-sectional scanning electron microscopy image of the fabricated CFPCF. It is observed that the magnitude of cross talk reached up to −206 dB over 0.8 mm length with a broad bandwidth of 282 nm at a central wavelength of 1790 nm. In addition, the polarization characteristics of the CFPCF including cross talk, central wavelength, and bandwidth can be adjusted by varying the diameter of the copper wire. It is shown that the resonance wavelength of the proposed filter can be tuned over the wide range of wavelengths from 1390 to 1890 nm. We have shown that by adjusting the copper wire diameter to 0.32Λ and 0.48Λ μm (Λ is pitch size), the proposed filter can operate at communication bands of 1310 and 1550 nm, respectively. The results suggest high-potential of the proposed fiber for polarization filtering and other sensing applications.

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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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