Negative curvature hollow core fibers: design, fabrication, and applications

Abstract

In this paper we consider a new type of hollow core microstructured optical fibers (HC MOFs) so called negative curvature hollow core fibers (NCHCFs). NCHCFs are known as hollow core fibers which allow to transmit a light under extremely high material loss of the cladding material. Such unique property of NCHCFs is due to the fact that their guiding mechanism is different from the guiding mechanisms in hollow core photonic crystal fibers (HC PCFs) and hollow core Bragg fibers (HC BFs). The two main factors which determine the guiding properties of NCHCFs are the 'negative curvature' (in a more general case, an alternating curvature) of the core -cladding boundary and the density of electromagnetic states of the cladding. It will be shown that the 'negative curvature' of the core -cladding boundary determines the type of interference which can lead to strong light localization in the air core. The interference which leads to air core mode formation in HC PCFs or HC BFs can be considered in terms of a linear momentum transfer by the photonic crystal cladding to the air core modes. In the case of NCHCFs the air core mode formation can be considered in terms of an azimuthal momentum transfer by the core -cladding boundary with an alternating curvature to the air core modes. The fabrication process of NCHCFs and several potential applications of NCHCFs in medicine, sensing and high power delivery are discussed.

Negative Curvature Hollow-Core Optical Fiber

“…Despite recent efforts in analytical analysis [46], the function of the core wall shape is not yet clear. It appears that both the properties of the high-index and of the low-index cladding modes are affected by the curvature.…”