Surface Plasmon Resonances in Sierpinski-Like Photonic Crystal Fibers: Polarization Filters and Sensing Applications.

William O F Carvalho,J R Mejía-Salazar

doi:10.3390/molecules25204654

William O F Carvalho, J R Mejía-Salazar

Open Access

https://doi.org/10.3390/molecules25204654

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Abstract

We investigate the plasmonic behavior of a fractal photonic crystal fiber, with Sierpinski-like circular cross-section, and its potential applications for refractive index sensing and multiband polarization filters. Numerical results were obtained using the finite element method through the commercial software COMSOL Multiphysics®. A set of 34 surface plasmon resonances was identified in the wavelength range from nm to nm. Subsets of close resonances were noted as a consequence of similar symmetries of the surface plasmon resonance (SPR) modes. Polarization filtering capabilities are numerically shown in the telecommunication windows from the O-band to the L-band. In the case of refractive index sensing, we used the wavelength interrogation method in the wavelength range from nm to nm, where the system exhibited a sensitivity of nm/RIU (refractive index unit). Due to the broadband capabilities of our concept, we expect that it will be useful to develop future ultra-wide band optical communication infrastructures, which are urgent to meet the ever-increasing demand for bandwidth-hungry devices.

Highlights

Surface plasmon resonances (SPRs) are enhanced electromagnetic fields bound to metal/dielectric interfaces through resonantly coupled optical and electronic excitations [1]
The cross-section of these surface plasmon resonance (SPR)-photonic crystal fibers (PCFs) are usually made by periodic arranges of air holes, some of which are filled or coated with metallic components, surrounding one or more cores
The interaction between nearby metallic scatterers increases the number of allowed resonances through plasmonic hybridization [46,47], i.e., the overlap of plasmonic near-fields between adjacent metallic scatterers, which resembles the electronic bands from well-localized atomic orbitals in solid state physics [48,49]

Summary

Introduction

Surface plasmon resonances (SPRs) are enhanced electromagnetic fields bound to metal/dielectric interfaces through resonantly coupled optical and electronic excitations [1]. The use of fractal geometries, on the other hand, has been successfully exploited during the last decades for the realization of multiband (or broadband) compact and high-performance antennas [34,35,36] These self-similar geometries have enabled multispectral compatibility and multiple applications when used for patterning one- and two-dimensional plasmonic superlattices [37,38,39,40,41]. We utilized a Sierpinski-like [42] geometry for the corresponding circular cross-section of the fiber, where one of the subsets in the fractal geometry was considered with metallic inclusions Using this fractal design we found a set of 34 plasmonic modes in the frequency range from 630 nm to 1700 nm, which enable applications from the visible to the infrared regime. Potential applications for high-performance refractive index sensing and for multiband polarization filters are shown here

PCF Design and Modeling

Results and Discussion

Conclusions