Mathematical Modelling of a 0.68/0.75 μm Optical Filter Based on Photonic Crystal Fibre and Au Surface Plasmon Resonance

The filter is designed with air holes distributed in a hexagonal shape, and in the core of the filter, there are four gold rods to achieve surface plasmon resonance (SPR). The effect of the air hole’s diameter and the hole-pitch (p) dimension on the effective mode area (X-polarization) and the Confinement Loss was studied using the finite element method (FEM). This analysis found evidence that the hole-pitch (p) is the most crucial factor that affects confinement loss value without shifting the resonant wavelength. In addition, increasing the air hole’s diameter (d) can affect the amount of power transferred by changing the refractive index and shifting the resonant wavelength toward longer wavelengths. Our results demonstrated that could attain a maximum confinement loss of 332.95 dB∕cm and a minimum effective mode area of 10.44 μm
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for p=1.9 μm and d= 1.2 μm at λ=0.75 μm. The control d (1.2, 1.3, 1.4, and 1.6) μm can be used to produce different induced resonant wavelengths (0.68, 0.7, 0.72, and 0.75) μm respectively. This filter has a lot of advantages, like being able to filter out wavelengths between 0.68 and 0.75 μm, and it can be used for a bunch of different things in biotech and medicine. Additionally, PCF has a simple structure and is simple to manufacture.