Orbital Angular Momentum Mode Propagation in a Hexagonal-Ring Core Spiral PCF

This research work proposes a photonic crystal fiber in which the air holes are structured in the shape of spiral. The material selected for background is fused silica. Operating wavelength is selected as 1550 nm. Hence, the refractive index of fused silica (1.444) is computed using Sellmeier coefficients. Finite Element Analysis is used for modal analysis and mode propagation in the fiber is studied. TE
0,1
, HE
2,1
, and TE
0,1
are identified. Further OAM mode propagation is studied and 2 OAM modes have successfully been shown to propagate. Multiple fiber parameters are further studied for TE
0,1
mode. Wavelength dependent effective refractive index is studied using Sellmeier coefficients and is observed to be monotonically decreasing with wavelength. In the wavelength range from 0.5-2.0µm, an all-anomalous dispersion is achieved for the PCF with values ranging from ~209 ps(km-nm)
⁻¹
to ~42 ps(km-nm)
⁻¹
. Imaginary refractive index dependent confinement loss is also studied. With values ranging from 1.87×10
⁻¹¹
m
²
at 0.5µm to 2.31×10
⁻¹¹
m
²
at 2µm, the effective area of the PCF is found to be increasing with wavelength. Nonlinearity is vastly influenced by effective area due to their inverse nature. Hence, nonlinearity is observed to be increasing in the wavelength window. Highest and lowest values achieved are 18.8 (Wkm)
⁻¹
and 3.79 (Wkm)
⁻¹