Slow Light Effect by Photonic Angular Momentum States

TL;DR

This paper demonstrates a novel slow light scheme using photonic angular momentum states in metamaterials, leveraging dark states with helical phase to achieve high group indices exceeding 500.

Contribution

It introduces a new approach to slow light by utilizing dark photonic angular momentum states with helical phase in metamaterials, distinct from traditional polarization-based methods.

Findings

Numerical simulations confirm the feasibility of the scheme.

Achieved high group index greater than 500.

Dark photonic AMSs cause transmission dips in high transmission windows.

Abstract

We show that the photonic angular momentum states (AMSs) in metamaterials can be utilized to achieve slow light. The photonic AMS possesses a helical phase, the orbital-angular-momentum degree of freedom in photons. Unlike the traditional slow-light schemes in metamaterials by using orthogonal polarizations, the photonic AMSs are dipole forbidden for all polarizations of free-space radiation due to the existence of helical phase. Numerical simulation for a metamaterial design proves the feasibility of this scheme, in which the indirectly excitation of dark photonic AMSs burns some transmission dips in the otherwise high transmission window. With the unique merits of dark photonic AMSs, this slow light scheme can realize a high group index $n_g$ greater than $\sim500$.