[Paper Review] Efficient Light Funneling based on the non-Hermitian Skin Effect

Sebastian Weidemann, Mark Kremer+6 more|arXiv (Cornell University)|Apr 4, 2020

Quantum Mechanics and Non-Hermitian Physics31 references87 citations

TL;DR

The paper demonstrates that engineering lattice anisotropy to induce a non-Hermitian skin effect in a large-scale photonic mesh causes light to be irresistibly funneled to an interface, regardless of excitation.

ABSTRACT

In the last two decades, the ubiquitous effect of dissipation has proven to entail astonishing non-Hermitian features, rather than just being an inescapable nuisance. As an alternative route to non-Hermiticity, we tailor the anisotropy of a lattice, which constitutes an, up to now, barely exploited degree of freedom. In this case, the appearance of an interface dramatically alters the entire eigenmode spectrum, leading to the exponential localization of all modes at the interface, which goes beyond the expectations for Hermitian systems. This effect is dubbed "non-Hermitian skin effect". We experimentally demonstrate it by studying the propagation of light in a large scale photonic mesh lattice. For arbitrary excitations, we find that light is always transported to the interface, realizing a highly efficient funnel for light.

Motivation & Objective

• Motivate non-Hermiticity as a design tool for photonic systems beyond dissipation.
• Explore how interface-induced spectral changes can localize all eigenmodes at the boundary.
• Demonstrate, experimentally, scalable light funneling in a large photonic lattice.

Proposed method

• Tailor lattice anisotropy to realize non-Hermitian skin effect in a photonic mesh.
• Study propagation of light for arbitrary excitations within the lattice.
• Experimentally observe exponential localization of eigenmodes at an interface.

Experimental results

Research questions

• RQ1 Can anisotropy-engineered non-Hermitian skin effect cause universal light funneling toward an interface?
• RQ2 Does the skin effect localize all eigenmodes at the interface in a large-scale photonic lattice?
• RQ3 How does the interface influence eigenmode spectrum and light transport for arbitrary excitations?

Key findings

• Light is transported to the interface for arbitrary excitations, acting as a highly efficient light funnel.
• Interface-induced non-Hermitian skin effect leads to exponential localization of all modes at the interface.
• Experimental demonstration is performed in a large-scale photonic mesh lattice.
• Non-Hermiticity is realized via anisotropy rather than dissipation as a design degree of freedom.