Broadband Multiple Topological Rainbows

Abstract

Topological photonics offers enhanced control over electromagnetic fields by providing a platform for robust trapping and guiding topological states of light. The topological rainbow can separate and distribute different wavelengths of topological photonic states into different positions, but related topological devices have not yet been fully explored. In this work, topological rainbows are realized by inserting a sandwiched gradient structure in the topological waveguide to realize the topological edge states. A robust one‐way slow‐light coupling state is realized to broaden the frequency range of the formed topological rainbow with the robust transmission. Thus, multiple topological rainbows are realized by combining the topological property with immunity to backscattering and coupling states of the slow light. Accordingly, light can spread, separate, and thus be trapped at different positions in different directions. This work provides a new way to reconfigure the topological rainbow and brings opportunities to study nanophotonic topological devices.

Multifunctional topological photonic crystal device for multichannel frequency routing and highly sensitive refractive index sensing

“…The band structures of the expanded and shrunken UCs possess the same bandgap with the frequency range, as shown in the first and third panels of figure 1(b). In contrast, the first and second bands are inverted, as can be seen from the eigenmode parities [20,21] at the high symmetric points of the first BZ, as shown from the field distribution of figure 1(c). The E z | | field distribution of UC1/UC4/UC5 at 1st and 2nd bands is mirrorsymmetrical/anti-symmetrical, while that of UC3/UC7 is inverted to be mirror anti-symmetrical/symmetrical.…”