# Chiral modes and directional lasing at exceptional points

@article{Peng2016ChiralMA, title={Chiral modes and directional lasing at exceptional points}, author={Bo Peng and Şahin Kaya {\"O}zdemir and Matthias Liertzer and Weijian Chen and Johannes Kramer and Huzeyfe Yılmaz and Jan Wiersig and Stefan Rotter and Lan Yang}, journal={Proceedings of the National Academy of Sciences}, year={2016}, volume={113}, pages={6845 - 6850} }

Significance Exceptional points (EPs) emerge when a system with loss or gain is tuned such that its eigenvalues and the corresponding eigenstates coalesce. By operating close to two EPs, we achieved a dynamic control of the rotation direction of light in a whispering-gallery-mode (WGM) resonator. This enabled us to tune the emission direction of a WGM microlaser from bidirectional, when the system is away from the EPs, to unidirectional emission at EPs and to reverse the emission direction by…

## 329 Citations

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## References

SHOWING 1-10 OF 51 REFERENCES

Loss-induced suppression and revival of lasing

- PhysicsScience
- 2014

Overturning conventional wisdom that loss is bad and should be minimized, Peng et al. show that carefully tweaking the coupling strength between the various components of a coupled optical system can actually result in an enhancement of the optical properties by adding more loss into the system.

Chiral nanophotonic waveguide interface based on spin-orbit interaction of light

- PhysicsScience
- 2014

It is demonstrated that the directional flow of light in a fiber can be controlled by placing a single gold nanoparticle on or near the surface of the fiber by exploiting the chiral properties of light (the spin-orbit interaction) to create a chiral waveguide coupler.

Structure of whispering-gallery modes in optical microdisks perturbed by nanoparticles

- Physics
- 2011

It is a well-known fact that a single nanoparticle placed in the evanescent field of an optical microdisk leads to coherent backscattering of light between counterpropagating whispering-gallery…

Controlled manipulation of mode splitting in an optical microcavity by two Rayleigh scatterers.

- PhysicsOptics express
- 2010

Rich dynamics and tunability of split modes in a single microresonator will find immediate applications in optical sensing, opto-mechanics, filters and will provide a platform to study strong light-matter interactions in two-mode cavities.

Local chirality of optical resonances in ultrasmall resonators.

- PhysicsPhysical review letters
- 2012

The results demonstrate that the local chirality of optical resonances can be utilized to control the output directionality and enhance the collection efficiency of emission from ultrasmall resonators.

Non-Hermitian-transport effects in coupled-resonator optical waveguides

- Physics
- 2014

Coupled-resonator optical waveguides are known to have interesting and useful dispersion properties. Here, we study the transport in these waveguides in the general case where each resonator is open…

Parity–time synthetic photonic lattices

- PhysicsNature
- 2012

The experimental observation of light transport in large-scale temporal lattices that are parity–time symmetric is reported and it is demonstrated that periodic structures respecting this symmetry can act as unidirectional invisible media when operated near their exceptional points.

Observation of unidirectional backscattering-immune topological electromagnetic states

- PhysicsNature
- 2009

It is demonstrated that, like their electronic counterparts, electromagnetic CESs can travel in only one direction and are very robust against scattering from disorder; it is found that even large metallic scatterers placed in the path of the propagating edge modes do not induce reflections.

Estimation of Purcell factor from mode-splitting spectra in an optical microcavity

- Physics
- 2011

We investigate scattering process in an ultrahigh-Q optical microcavity coupled to subwavelength scatterers by introducing splitting quality Q{sub sp}, a dimensionless parameter defined as the ratio…

Spawning rings of exceptional points out of Dirac cones

- PhysicsNature
- 2015

The results indicate that the radiation existing in any open system can fundamentally alter its physical properties in ways previously expected only in the presence of material loss and gain.