Strong circular dichroism in twisted single-ring hollow-core photonic crystal fiber

TL;DR

This paper demonstrates strong circular dichroism in twisted single-ring hollow-core photonic crystal fibers, enabling efficient circular polarization filtering with potential applications in UV light generation and polarizing components.

Contribution

The study introduces a novel twisted SR-PCF design that achieves high circular dichroism and polarization selectivity through helical Bloch modes and birefringence effects.

Findings

Strong circular dichroism observed in twisted SR-PCF

High loss for one circular polarization, efficient transmission for the other

Potential for circular polarizer applications in UV regimes

Abstract

We report a series of experimental, analytical and numerical studies demonstrating strong circular dichroism in helically twisted hollow-core single-ring photonic crystal fiber (SR-PCF), formed by spinning the preform during fiber drawing. In the SR-PCFs studied, the hollow core is surrounded by a single ring of non-touching capillaries. Coupling between these capillaries results in the formation of helical Bloch modes carrying orbital angular momentum. In the twisted fiber, strong circular birefringence appears in the ring, so that when a core mode with a certain circular polarization state (say LC) phase-matches to the ring, the other (RC) is strongly dephased. If in addition the orbital angular momentum is the same in core and ring, and the polarization states are non-orthogonal (e.g., slightly elliptical), the LC core mode will experience high loss while the RC mode is efficiently transmitted. The result is a single-circular-polarization SR-PCF that acts as a circular polarizer over a certain wavelength range. Such fibers have many potential applications, for example, for generating circularly polarized light in gas-filled SR-PCF and realizing polarizing elements in the deep and vacuum ultraviolet.