Robust Circularly Polarized Luminescence via Quasi-Bound States in the Continuum in Intrinsic Chiral Silicon Metasurfaces

TL;DR

This paper demonstrates robust circularly polarized light emission from achiral dye molecules using silicon metasurfaces that support quasi-BICs and surface lattice resonances, with implications for chiral light-matter interactions.

Contribution

It introduces a method to achieve stable circularly polarized luminescence via quasi-BICs in silicon metasurfaces, highlighting the role of layer thickness and mode confinement.

Findings

Quasi-BIC mode maintains high dissymmetry factor despite emission angle variations.

Surface lattice resonance mode shows sign inversion depending on emission energy.

Layer thickness significantly influences the polarization characteristics of emitted light.

Abstract

We demonstrate a circularly polarized photoluminescence emission, with dissymmetry factors $g_\mathrm{PL}$ over 0.1, from achiral organic dye molecules by leveraging quasi-bound states in the continuum (quasi-BICs) and surface lattice resonances (SLRs) in intrinsic silicon chiral metasurfaces. We find that the $g_\mathrm{PL}$ associated with the quasi-BIC mode remains robust against variations in emission angle and dye thickness owing to its strong lateral field confinement. In contrast, the $g_\mathrm{PL}$ of the SLR mode exhibits sign inversion depending on the emission energy and dye layer thickness. The experimental results are supported by mode decomposition analysis, helicity density analysis, and near-field spatial distribution of the electric field. These findings illustrate the relevance of the emitter's layer thickness in optimizing the emission of circularly polarized light. They also elaborate on the robustness of chiral quasi-BICs, offering insights into chiral light-matter interactions and advancing the design of circularly polarized light-emitting devices.