Dual-band topological rainbows in Penrose-triangle photonic crystals

Topological rainbows (TRs) possess the potential to separate and localize topological photonic states across different frequencies. However, previous works on TRs have been confined to a single-frequency band. Furthermore, the achievement of multiband TRs within a single structure is still a significant challenge. In this paper, a composed structure waveguide is designed based on Penrose-triangle photonic crystals. By adjusting the size of scatterers and introducing non-Hermitian terms, we successfully realize dual-band TRs. This achievement will not only enhance the uniformity of the electric field intensity distribution but also provide the potential to introduce a new avenue for the development of robust photonic devices dedicated to processing vast amounts of data information.