Non-Hermitian engineering of terahertz light using exceptional points in electrically tuneable collective light-matter interactions

TL;DR

This paper demonstrates the electrical tuning of exceptional points in light-matter interactions at terahertz frequencies, enabling topological control of light properties and opening new avenues for dynamic terahertz optoelectronics.

Contribution

It introduces an electrically controllable system exhibiting exceptional points in terahertz light-matter interactions at room temperature, previously unobserved in such systems.

Findings

Electrical control of terahertz pulse phase and intensity via exceptional points

Reconstruction of the Riemann surface for complex energy landscape

Topological control of light through loss-imbalance and frequency detuning

Abstract

The topological structure associated with the branchpoint singularity around an exceptional point (EP) provides new tools for controlling the propagation of electromagnetic waves and their interaction with matter. To date, observation of EPs in light-matter interactions has remained elusive and has hampered further progress in applications of EP physics. Here, we demonstrate the emergence of EPs in the electrically controlled interaction of light with a collection of organic molecules in the terahertz regime at room temperature. We show, using time-domain terahertz spectroscopy, that the intensity and phase of terahertz pulses can be controlled by a gate voltage which drives the device across the EP. This fully electrically-tuneable system allows reconstructing the Riemann surface associated with the complex energy landscape and provides a topological control of light by tuning the loss-imbalance and frequency detuning of interacting modes. We anticipate that our work could pave the way for new means of dynamic control on the intensity and phase of terahertz field, developing topological optoelectronics, and studying the manifestations of EP physics in the quantum correlations of the light emitted by a collection of emitters coupled to resonators.