Confinement Loss in Hollow-Core Negative Curvature Fiber: a Multi-Layered Model

TL;DR

This paper introduces a multi-layered model to clarify the physical mechanisms behind light confinement in hollow-core negative curvature fibers, aiding both understanding and future fiber design.

Contribution

It develops a novel multi-layered model that quantifies four physical guidance mechanisms in NCF, providing new insights into their roles in light confinement.

Findings

Identifies four physical origins of light confinement in NCF.

Quantifies contributions of Fresnel transmission, near-grazing incidence, multi-path interference, and wall shape.

Provides a framework for designing improved hollow-core fibers.

Abstract

Simple structures are always a pursuit but sometimes not easily attainable. It took researchers nearly two decades for conceiving the structure of single-ring hollow-core negative curvature fiber (NCF). Recently NCF eventually approaches to the centre of intense study in fiber optics. The reason behind this slow-pace development is, undoubtfully, its inexplicit guidance mechanism. This paper aims at gaining a clear physical insight into the optical guidance mechanism in NCF. To clarify the origins of light confinement, we boldly disassemble the NCF structure into several layers and develop a multi-layered model. Four physical origins, namely single-path Fresnel transmission through cascaded interfaces, near-grazing incidence, multi-path interference caused by Fresnel reflection, and glass wall shape are revealed and their individual contributions are quantified for the first time. Such an elegant model could not only elucidate the optical guidance in existing types of hollow-core fibers but also assist in design of novel structure for new functions.