Non-Hermitian systems host exotic phenomena absent in their Hermitiancounterparts. One of the most striking examples is the non-Hermitian skin effect, in which a large number of eigenmodes become localized near a system boundary. Another phenomenon of growing interest is the self-healing effect, where a wave can recover its original profile after passing through a disturbance. Understanding how these effects can be controlled in realistic platforms is important for both fundamental physics and future photonic applications.
In this context, researchers from the University of Science and Technology of China proposed and numerically demonstrated an approach for manipulating skin modes in photonic Floquet lattices. They introduced the concept of skin mode tunability (SMT)—the mechanism in which the spectrum of skin modes localized at one boundary can be tuned via a potential applied at the opposite boundary.
The researchers showed that, despite its strong spatial localization, a skin mode can remain highly sensitive to perturbations at the far boundary because of the biorthogonal nature of non-Hermitian systems. By adjusting the boundary potential, a specific skin mode can be spectrally isolated from the other states, turning it into a self-healing state (SHS). Unlike typical skin modes, the SHS reconstructs its profile after encountering a disturbance, as it acquires the largest imaginary part of the eigenenergy and therefore dominates during propagation.
Building on this concept, the researchers designed an experimentally feasible implementation in a waveguide array and demonstrated the SMT. Guided by these theoretical results, they then simulated a photonic Floquet lattice of coupled helical waveguides using the beam propagation method (BPM) with experimentally realistic parameters. The results showed that, after appropriate boundary tuning, the target skin mode could recover its transverse profile after a local perturbation, demonstrating clear self-healing behavior.
The study provides a proof of concept for controlling wave dynamics through local boundary modulation in non-Hermitian photonic systems. Although direct experimental realization remains challenging because of long propagation distances and optical loss, the researchers suggest that stronger coupling and tailored gain-loss designs could facilitate the experimental observation of the effect.
From an application perspective, the work offers a practical framework for steering the energy and localization of skin modes through boundary perturbations. More broadly, the selective tuning of a single skin mode via boundary potentials could support functional designs, such as mode-selective routing, reconfigurable mode filters, and optical switches.
