Fig. 3: Photonic valley multiplexer.
From: Chiral valley edge states based on Dirac mass engineering
a Spatial distributions of \({m}_{K}\left({{\bf{r}}}\right)\) and \({m}_{{K}^{{\prime} }}\left({{\bf{r}}}\right)\), forming two bending waveguides for K- and K’-valley waves, respectively. These two bending waveguides together form the valley multiplexer. b Photonic valley multiplexer. This multiplexer is composed of three types of topological photonic crystals (CPC-1, CPC-2, and VPC-1), realized based on the spatially superposed mass distributions in (a). Insets: Edge dispersion for each domain wall channel. c, d Simulated field profiles when electromagnetic waves are incident from Port 1 and Port 3, respectively. Waves with different valley-polarizations converge into the horizontal bus waveguide without valley flipping. e, f Simulated and measured transmission spectra, reflecting the strong isolation between the K- and K’-valley channels.
