Optimal width of quasi-crystalline slabs of dielectric cylinders to light transmission contrast

TL;DR

This study investigates how the width of quasi-crystalline slabs of dielectric cylinders affects light transmission contrast, revealing optimal conditions for maximum contrast and the role of resonances in transmission behavior.

Contribution

It provides experimental and numerical analysis of the optimal slab width for enhanced light transmission contrast in quasi-crystalline dielectric structures.

Findings

Maximum transmission contrast occurs at a slab width of about three times the wavelength.

Resonances of photonic molecules mediate transmission in the band gap.

Thin slabs become transparent except at specific resonances, acting like absorbing molecules.

Abstract

Light confinement induced by resonant states in aperiodic photonic structures are interesting for many applications. A particular case of these resonances can be found in 2D quasi-crystalline arrangements of dielectric cylinders. These systems present a rather isotropic band gap as well as isolated in-gap photonic states (as a result of spatially localized resonances). These states are built by high symmetry polygonal clusters that can be regarded as photonic molecules. In this paper we study the transmission properties of a slab of glass cylinders arranged in approximants of decagonal quasi-crystalline structure. In particular, we investigate the influence of the slab width in the transmission contrast between the states and the gap. The study is both experimental and numerical in the microwave regime. We find that the best transmission contrast is found for a width of around 3 times the radiation wavelength. The transmission at the band gap region is mediated by the resonances of the photonic molecules. If the samples are thin enough they become transparent except around a resonance of the photonic molecule which reflects the incoming light. In this case the behavior is reminiscent of an absorbing molecule.