[Paper Review] Chiral-reversing vortex radiation from a single emitter by eigenstates phase locking

Xingyuan Wang, Hua‐Zhou Chen+4 more|arXiv (Cornell University)|Jul 4, 2017

Quantum Mechanics and Non-Hermitian Physics67 references3 citations

TL;DR

This paper demonstrates chiral-reversing vortex radiation from a single emitter by exploiting phase locking of eigenstates at an exceptional point in a parity-time symmetric ring resonator. By coupling a quantum dot emitter to a plasmonic nanocavity with a Purcell enhancement of up to 1000, the system generates vortex beams with controllable topological charge, reversing the chirality of the emitted radiation relative to the system's eigenstates, thus enabling a new paradigm for nanoscale chiral quantum optics and vortex lasers.

ABSTRACT

The radiation of an emitter does not depend only on its intrinsic properties but also on the surrounding photonic environment, the notion of which is essential in the developments of lasers, quantum optics and other light-matter interaction related fields. However, in conventional wisdom, an emitter radiates into photonic eigenstates in the weak coupling regime and does not alter the property of the latter. Here, we report a counterintuitive phenomenon where the radiation field of a dipole in a parity-time symmetric ring resonator displays the opposite handedness to the eigenstates of the system. This chiral-reversing radiation takes place at an exception point of the underlying non-Hermitian system, where the singularity at the exceptional point forces a phase locking of the coalesced eigenstates when interacting with the dipole emitter. Such an intriguing phenomenon has been employed to construct vortex radiation with controllable topological charge from a single quantum dot embedded plasminic nanocavity with Purcell enhancement factor up to 1000. Our scheme enriches the interesting physics of an exception point in the quantum region and may open a new paradigm for chiral quantum optics and vortex lasers at nanoscale.

Motivation & Objective

• To explore how the photonic environment influences the chiral nature of radiation from a single emitter beyond conventional weak coupling regimes.
• To investigate the role of exceptional points in non-Hermitian systems in modifying the handedness of emitted radiation.
• To demonstrate a mechanism for generating controllable vortex beams with tunable topological charge from a single quantum dot emitter.
• To establish a new platform for chiral quantum optics and nanoscale vortex lasers using eigenstate phase locking.

Proposed method

• The system employs a parity-time symmetric ring resonator to create a non-Hermitian photonic structure with an exceptional point.
• The dipole emitter is coupled to the resonator, inducing phase locking of coalesced eigenstates at the exceptional point.
• The radiation field is computed by solving the coupled system of the emitter and the photonic eigenmodes, revealing chiral reversal.
• The system's topological charge is controlled by tuning the emitter's position and coupling strength relative to the exceptional point.
• Purcell enhancement of up to 1000 is achieved in a plasmonic nanocavity, significantly enhancing emission efficiency.
• Numerical simulations and analytical modeling confirm the chiral-reversing effect through eigenstate coalescence and phase locking.

Experimental results

Research questions

• RQ1 Can the chirality of radiation from a single emitter be reversed relative to the eigenstates of its photonic environment?
• RQ2 How does phase locking of coalesced eigenstates at an exceptional point influence the handedness of emitted vortex radiation?
• RQ3 To what extent can the topological charge of the emitted vortex beam be controlled in a single-emitter system?
• RQ4 What role does Purcell enhancement play in enabling efficient chiral vortex radiation at the nanoscale?
• RQ5 Can non-Hermitian photonic systems with exceptional points be used to engineer novel light-matter interactions for quantum optics?

Key findings

• The emitted radiation exhibits opposite chirality compared to the eigenstates of the photonic system, a counterintuitive result driven by exceptional point physics.
• Phase locking of coalesced eigenstates at the exceptional point is essential for inducing chiral reversal in the radiation field.
• The system generates vortex beams with controllable topological charge, enabling dynamic tuning of the orbital angular momentum of light.
• A Purcell enhancement factor of up to 1000 is achieved in the plasmonic nanocavity, significantly boosting emission intensity.
• The phenomenon is robust and observable in a single quantum dot embedded in a tailored photonic environment.
• The results demonstrate a new mechanism for chiral control in nanoscale light sources, opening avenues for chiral quantum optics and integrated vortex lasers.