Uniform Chiral Near‐Fields in Achiral Nanocavity Induced by Magnetic Polaritons Mode

Abstract

Chiral near-fields are crucial in the analysis of chiral molecules, circularly polarized luminescence, and sensing. Under circularly polarized light illumination, left-and right-handed chiral near-fields occur around nanostructures. However, most previously reported works require structural chirality based on asymmetric 3D nanostructures. Usually, left-and right-handed chiral near-fields are difficult to separate in space, leading to low efficiency in applications. Here, achiral U-shaped groove nanostructure arrays are proposed to generate uniform chiral near-fields under circularly polarized light illumination. In contrast to vertical parallel plate nanostructures, a bottom layer is added below the two vertical parallel plates to design U-shaped groove nanostructures that induce magnetic polaritons mode. In the cavity of the achiral U-shaped groove nanostructure, chiral near-field is induced by the excitation of electric and magnetic near-fields with parallel components. These chiral near-fields strongly depend on the structural parameters of the U-shaped groove nanostructure. In addition, chiral molecules are introduced into the cavity of the U-shaped groove nanostructure to utilize it as sensors for chiral molecular detection. Numerical results show that the circular dichroism of the molecules is enhanced remarkably. These findings pave the way toward the development of practical and scalable platforms for new chiroptical applications.