Direct Observation of Topological Edge States in Silicon Photonic Crystals

The concept of topology has proven immensely powerful in physics, describing new phases of matter with unique properties. There has been a recent surge in attempts to implement topological protection in the photonic domain, owing to the application potential of robust transport immune to scattering at disorder. A famous class of electronic topological insulators relies on the quantum spin-Hall effect (QSHE). Photonic analogues of QSHE were recently predicted to occur in photonic crystals with special symmetries [1,2]. Interestingly, topological photonic crystals employing QSHE offer the possibility to access their properties via far-field radiation [3].