Multiband adjustment engineering strategy for broadband range in photonic crystals

• A multifunctional double-layer nested photonic crystal structure was developed. • The influence of the rotation process of photonic crystals on topological energy bands were summarized and studied. • The topological boundary state effect and degree of freedom were improved by experiment. • Photonic crystal-based devices can be used for gradient band transmission. • A photonic crystal was developed to achieved high-order topological states in the broadband range of X-band. Topological edge states are crucial for optical modulation, and the overlapping Brillouin zones in nested structures can effectively control multiband edge states. A nested photonic crystal framework can enhance the rotational freedom, providing additional functionalities. In this study, a multifunctional, tunable, innovative double-rotation C 4 nested photonic crystal structure was developed; it reached a higher degree of freedom via double independent rotations. These nested C 4 photonic crystal structures could expand the functional range of C 4 structure implementation. The multifunctional implementation of multienergy band transmissions, unidirectional transmissions, and wavelength division multiplexers containing nested C 4 structures were experimentally demonstrated. The experimental results agreed well with the simulated predictions. Thus, this study offers new insights and strategies to foster the advancement of topological photonics and radar communication devices.