Source-linked AI summary
Electromagnetically induced transparency at a chiral exceptional point
Changqing Wang, Xuefeng Jiang, Guangming Zhao, Mengzhen Zhang, Chia Wei Hsu, Bo Peng, A. Douglas Stone, Liang Jiang, Lan Yang
TL;DR
The paper addresses how to connect optical-state manipulation with light-flow and spectral control without relying solely on continuous parameters. It theoretically and experimentally studies indirectly coupled WGM microresonators tuned to exceptional points, finding that opposite eigenstate chiralities produce absorption or transparency and can serve as discrete control states.
Problem
An explicit physical scheme connecting optical-state manipulation with control of light flow and spectra was lacking, beyond continuous controls such as temperature or optical power.
Method
The authors directly construct electromagnetically induced transparency in an indirectly coupled WGM microresonator system and tune one resonator to exceptional points with opposite chiralities.
Results
Opposite exceptional-point chiralities modulate the optical response: EP− produces absorption features, whereas EP+ produces transparency through phase-controlled loop interference.
Takeaways & Limitations
Discrete optical states with chirality 1 or -1 provide one bit of information storage that can act as a control state for manipulating light flow and spectra.
Takeaways & Limitations
The level-structure analysis assumes γ1,1 ≪ γ1,2, allowing one decay or coupling contribution to be neglected.
Abstract
from arXiv · showhide
Electromagnetically induced transparency, as a quantum interference effect to eliminate optical absorption in an opaque medium, has found extensive applications in slow light generation, optical storage, frequency conversion, optical quantum memory as well as enhanced nonlinear interactions at the few-photon level in all kinds of systems. Recently, there have been great interests in exceptional points, a spectral singularity that could be reached by tuning various parameters in open systems, to render unusual features to the physical systems, such as optical states with chirality. Here we theoretically and experimentally study transparency and absorption modulated by chiral optical states at exceptional points in an indirectly-coupled resonator system. By tuning one resonator to an exceptional point, transparency or absorption occurs depending on the chirality of the eigenstate. Our results demonstrate a new strategy to manipulate the light flow and the spectra of a photonic resonator system by exploiting a discrete optical state associated with specific chirality at an exceptional point as a unique control bit, which opens up a new horizon of controlling slow light using optical states. Compatible with the idea of state control in quantum gate operation, this strategy hence bridges optical computing and storage.
constructive or destructive.
The indirectly coupled WGM microresonator system exhibits different transmission behavior when μR1 is steered to exceptional points with opposite chiralities. Experiments and simulations examine absorption at EP− and transparency at EP+ while varying coupling gaps and phase.
- EP− absorption: μR1 is steered to EP− with chirality -1 and a CCW eigenmode, where backscattering from CCW to CW is absent.This breaks the coupling between the two resonators through μR1.
- EP+ transparency: μR1 is steered to EP+ with chirality 1 and a CW eigenmode, allowing coupling between level ω1,EP+ and ω2,±.The corresponding level structure can be regarded as two sets of Λ-type levels when γ1,1 ≪ γ1,2.
- EP+ transparency: The EP+ response is characterized experimentally and numerically by varying the μR1–μR2 distance, taper–μR1 gap, and phase θ.The simulations include transmission at zero detuning T(Δ = 0) as a function of θ or taper-cavity gap change.