Dispersion-tunable photonic topological waveguides

Dispersion-tunable photonic topological waveguides have recently attracted much attention, due to their promising applications on topological devices with tunable operational frequencies. Since dispersions of topological waveguides traverse the whole bandgaps of bulk structures, tuning the dispersions (especially the bandwidths) requires changing the whole bulk of corresponding photonic topological insulators. A previously reported material-modification approach provided a parallel tuning on such numerous lattices; however, the increased material loss deteriorated transmissions of the topological waveguide. Here, a parallel tuning approach on structures is theoretically proposed and demonstrated, which spawns dispersion-tunable photonic topological waveguides without increasing material loss. Based on the bilayer honeycomb model, a topological valley waveguide by utilizing bilayer designer plasmonic structures is constructed, accomplished with dispersion tunings by altering interlayer distance. Experimental results validate the theoretical model and display a 61%-relative-tuning range of frequency, with a tunable relative bandwidth up to 16%. This approach may promise applications in tunable topological lasers, robust delay lines, and intelligent photonic devices.