Design of an Ultrahigh Birefringence Photonic Crystal Fiber with Large Nonlinearity Using All Circular Air Holes for a Fiber-Optic Transmission System

Shovasis Biswas,Md Islam,Mohammad Mia,S Islam,Summit Sayem,Feroz Ahmed

doi:10.3390/photonics5030026

Shovasis Biswas, Md Islam + Show 4 more

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https://doi.org/10.3390/photonics5030026

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Abstract

This paper proposes a hexagonal photonic crystal fiber (H-PCF) structure with all circular air holes in order to simultaneously achieve ultrahigh birefringence and high nonlinearity. The H-PCF design consists of an asymmetric core region, where one air hole is a reduced diameter and the air hole in its opposite vertex is omitted. The light-guiding properties of the proposed H-PCF structure were studied using the full-vector finite element method (FEM) with a circular perfectly matched layer (PML). The simulation results showed that the proposed H-PCF exhibits an ultrahigh birefringence of 3.87 × 10−2, a negative dispersion coefficient of −753.2 ps/(nm km), and a nonlinear coefficient of 96.51 W−1 km−1 at an excitation wavelength of 1550 nm. The major advantage of our H-PCF design is that it provides these desirable modal properties without using any non-circular air holes in the core and cladding region, thus making the fiber fabrication process much easier. The ultrahigh birefringence, large negative dispersion, and high nonlinearity of our designed H-PCF make it a very suitable candidate for optical backpropagation applications, which is a scheme for the simultaneous dispersion and nonlinearity compensation of optical-fiber transmission links.

Highlights

Photonic crystal fibers (PCF) recently drew significant attention, as they exhibit extraordinary optical characteristics such as high birefringence, large effective mode area, high nonlinearity, and very low confinement loss as compared to other conventional optical fibers [1,2,3]
PCFs with high-index cores were shown to exhibit similar features to conventional optical fibers, where the light-guiding properties are largely based on a physical mechanism called total internal reflection (TIR)
This study reported a high birefringence of 2.22 × 10−2, a large nonlinearity of 68 W−1 km−1, and confinement losses on the order of 10−4 dB/m [21]

Summary

Introduction

Photonic crystal fibers (PCF) recently drew significant attention, as they exhibit extraordinary optical characteristics such as high birefringence, large effective mode area, high nonlinearity, and very low confinement loss as compared to other conventional optical fibers [1,2,3]. PCFs with high-index cores were shown to exhibit similar features to conventional optical fibers, where the light-guiding properties are largely based on a physical mechanism called total internal reflection (TIR). In order to achieve TIR in conventional fibers, a higher refractive index of the core compared to the surrounding media is required. Photonic bandgap (PBG) materials were realized for localizing and controlling light in cavities and waveguides. Structured materials such as PCFs exhibit the PBG property, since certain photonic bandgaps may be forbidden by selectively choosing the lattice structure and dimensions within the crystal [4]

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