Observation of non-Hermitian topology from optical loss modulation

TL;DR

This paper experimentally demonstrates that non-Hermitian topology can arise solely from loss modulation in a photonic system, revealing a new way to engineer topological properties through loss engineering.

Contribution

The work shows that topological features can originate purely from non-Hermiticity due to loss modulation, using a programmable photonics platform to realize a non-Hermitian Aubry-Andre-Harper model.

Findings

Topological edge modes emerge from loss modulation.

Edge modes are resilient to disorder.

Loss engineering can generate topological properties.

Abstract

Understanding the interplay of non-Hermiticity and topology is crucial given the intrinsic openness of most natural and engineered systems and it has important ramifications in topological lasers and sensors. Intense efforts have been devoted to unveiling how non-Hermiticity may impact the most significant features of topological systems, but only recently it has been theoretically proposed that topological features could originate solely from the system's non-Hermiticity in photonic systems. In this work, we experimentally demonstrate the appearance of non-Hermitian topology exclusively from loss modulation in a photonic system that is topologically trivial in the absence of loss. We do this by implementing a non-Hermitian generalization of an Aubry-Andre-Harper model with purely imaginary potential in a programmable integrated photonics platform, which allows us to investigate different periodic and quasi-periodic configurations of the model. In both cases, we show the emergence of topological edge modes and explore their resilience to different kinds of disorder. Our work highlights loss engineering as a mechanism to generate topological properties.