Crossed chiral band approximation for wideband self-collimation of light

TL;DR

This paper introduces a novel approach using band crossing and chiral band approximation to achieve wideband, defect-free self-collimation in low-symmetry photonic structures, enabling broadband light guidance with high angular tolerance.

Contribution

It presents a new design methodology for broadband self-collimation in photonic structures through band crossing and chiral approximation, demonstrating high fractional bandwidths and all-angle collimation.

Findings

Achieved fractional bandwidths of 0.35 and 0.37 for specific radii.

Demonstrated all-angle collimation up to 80 degrees.

Validated performance through transmission, E-field, band diagrams, and group velocity analysis.

Abstract

We propose a perspective to the evaluation of the wide bandwidth phenomenon, by introducing the band tailoring and chiral band approximation on the self-collimation effect for low-symmetric photonic structures. In the case of the crossing of the bands, we claim the excitation of the lower mode can provide the utilization of the entire bandwidth by suppressing the intersection regions where the frequencies tend to mix. Thereby, we design broadband self-collimation capable, defect-free photonic structures and examine their performances. A fractional bandwidth of $0.35$ (${a}\backslash{\lambda}=0.429-0.607$) and $0.37$ (${a}\backslash{\lambda}=0.481-0.701$) are achieved for radii of ${r}=0.25{a}$ and ${r}=0.23{a}$, respectively. We explore the full-range collimation using transmission and E-field intensity analysis in addition to band diagrams and group velocity dispersions. Moreover, we indicate all-angle collimation validity even for highly tilted sources up to an angle of $80^\circ$.