Photonic topological phase transition induced by material phase transition

TL;DR

This paper demonstrates a novel method to induce and control topological phase transitions in two-dimensional photonic insulators using phase-change material nanopatterns, enabling reconfigurable photonic circuits.

Contribution

It introduces a new approach to dynamically alter photonic topological phases via phase transition of GST nanopatterns, a first in the field.

Findings

First experimental observation of photonic topological phase transition via material phase change.

Successful control of topological invariants through symmetry-breaking perturbations.

Reconfigurable photonic properties demonstrated with ultrafine lithography techniques.

Abstract

Photonic topological insulators (PTIs) have been proposed as an analogy to topological insulators in electronic systems. In particular, two-dimensional PTIs have gained attention for the integrated circuit applications. However, controlling the topological phase after fabrication is difficult because the photonic topology requires the built-in specific structures. This study experimentally demonstrates the band inversion in two-dimensional PTI induced by the phase transition of deliberately-designed nanopatterns of a phase-change material, Ge2Sb2Te5 (GST), which indicates the first observation of the photonic topological phase transition with changes in the Chern number. This approach allows us to directly alter the topological invariants, which is achieved by symmetry-breaking perturbation through GST nanopatterns with different symmetry from original PTI. The success of our scheme is attributed to the ultrafine lithographic alignment technologies of GST nanopatterns. These results demonstrate to control photonic topological properties in a reconfigurable manner, providing an insight into new possibilities for reconfigurable photonic processing circuits.