Supermode resonances in a multi-core holey fiber-based sensor

Abstract

The propagation characteristics in a new multi-core holey fiber-based sensor are investigated using a finite element method. The fiber is made by an air hole in the center of the structure, six air holes which are placed at the vertices of a hexagon, two layers of air holes arranged in a hexagonal way between which two large air hole on the horizontal line, four or seven small air holes which are infiltrated between some small air holes and are inserted in a silica core which is surrounded by a gold layer, and by a water layer which can be considered infinite for the numerical model. The four supplementary holes impede the resonant interaction (0.595 μm) between one of the pair of twofold degenerate supermode with a plasmon mode from the previously published sensor structure and introduces two new supermodes in resonance with the plasmon modes when the loss matching (0.597 μm and 0.599 μm) conditions are satisfied. By adding only four air holes and enlarge the radius of two existing hole produces a stronger transmission loss (856.2 dB/cm and 937.5 dB/cm) of a guided supermode at the resonant coupling due to efficient interaction with a plasmon mode near the loss matching points. The advantages of the configuration with seven small air holes where there is a resonance between two supermodes, are a better spectral resolution and higher amplitude sensitivity.