Giant red shift and enhancement of resonant light confinement in planar array of dielectric bars

TL;DR

This research uncovers high Q-factor trapped mode resonances with significant red shifts in a planar array of dielectric bars, enabling advanced resonant structure design using moderate refractive index materials.

Contribution

First demonstration of high Q-factor trapped mode resonances with large red shifts in dielectric bar arrays, highlighting strong coupling effects and design potential.

Findings

High Q-factor trapped mode resonances were observed.

Significant red shift of resonant wavelength due to strong coupling.

Decreasing asymmetry increases red shift and Q-factor.

Abstract

Results of research of resonant phenomena in planar periodic structures consisted of dielectric elements are presented. A problem of plane wave diffraction by a structure which a periodic cell is composed of two dielectric bars with different lengths has been solved. For the first time an existence of high Q-factor trapped mode resonances are revealed in these structures. The main difference of studied structure in contrast to the planar structure with a single dielectric bar in the unit cell is appearing of a great red shift of a trapped mode resonant wavelength. The red shift is caused by strong coupling of electromagnetic fields in neighbor dielectric bar resonators. This property is very attractive to design resonant periodic planar structures by using moderate refractive index materials like semiconductors within their transparency window. In the near infrared band, the trapped mode resonances of periodic planar structure with bars made of germanium have been studied. It is shown that decreasing of structure asymmetry degree results in increasing of both red shift and Q-factor of resonance.