Light stops at exceptional points

Abstract

Almost twenty years ago the light was slowed down to less than $10^{-7}$ of its vacuum speed in a cloud of ultracold atoms of sodium. Upon a sudden turn-off of the coupling laser, a slow light pulse can be imprinted on cold atoms such that it can be read out and converted into photon again. In this process, the light is stopped by absorbing it and storing its shape within the atomic ensemble. Alternatively, the light can be stopped at the band edge in photonic-crystal waveguides, where the group speed vanishes. Here we extend the phenomenon of stopped light to the new field of parity-time (PT) symmetric systems. We show that zero group speed in PT symmetric optical waveguides can be achieved if the system is prepared at an exceptional point, where two optical modes coalesce. This effect can be tuned for optical pulses in a wide range of frequencies and bandwidths, as we demonstrate in a system of coupled waveguides with gain and loss.

5 pages, 4 figures

References in corpus (6)

• Making Sense of Non-Hermitian Hamiltonians
• The physics of exceptional points
• Loss-induced suppression and revival of lasing
• Visualization of Branch Points in PT-Symmetric Waveguides
• Stationary pulses of light in an atomic medium
• Dynamical Observations of Self-Stabilising Stationary Light

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• Exceptional Points in the Flatland: A Non-Hermitian Line-Wave Scenario
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• Higher order topological degeneracies and towards unique successive state-switching in a four-level open system
• Indirect link between resonant and guided modes on uniform and periodic slabs
• High-order spectral singularity
• Edge and bulk dissipative solitons in modulated PT-symmetric waveguide arrays
• Anomalous mechanisms of the loss of observability in non-Hermitian quantum models
• Revisit the Poynting vector in PT-symmetric coupled waveguides
• Non-Hermitian guided modes and exceptional points using loss-free negative-index materials
• Apodized photonic crystals: A non-dissipative system hosting multiple exceptional points
• Quantum phase transitions mediated by clustered non-Hermitian degeneracies
• Transport characteristics of a $\mathcal{P}\mathcal{T}$-symmetric non-Hermitian system: Effect of environmental interaction