Topological photonic crystals in the visible: design and angle-resolved characterization of the bulk and edge states

We fabricated and characterized photonic crystals with non-trivial topological bulk states and pseudo-time-reversal-symmetry protected helical edge states in the visible regime. Hexagonal silicon photonic crystals with a lattice constant of 450nm were fabricated on 10nm Si₃N₄ membranes utilizing electron beam lithography and reactive ion etching. With a 30-keV electron beam, we excite coherent cathodoluminescence in the nanostructured material and derive photonic band structures based on angles as well as frequencies of the emitted light. Further investigation into polarization states of the emitted light with both plane wave excitation and electron beam excitation reveal edge states that are pseudo-spin orbit coupled.