Photonic twistronics-induced broadband omnidirectional perfect transparency

Omnidirectional perfect transparency (OPT) in materials is very useful in many applications. Traditional systems face challenges in achieving OPT owing to the fact that the propagating phase changes with the incident angles. Previous methods of realizing OPT are constrained by complex electromagnetic interactions and restricted to a single frequency, which limits the applications of OPT. In this study, inspired by the field of twistronics in photonics, we propose a twisted structure composed of alternating two kinds of tilted anisotropic metamaterials (TAMs), with the optical axis rotated in opposite directions to realize broadband OPT. These TAMs are effectively obtained by rotating multilayers composed of two kinds of deep-subwavelength dielectric through equal angles in opposite directions. As the incident angles increase, the variations of the propagating phases in the two kinds of TAMs are opposite. This phase variation compensation effect makes the total propagating phase in the structure angle-independent, leading to the omnidirectional zero-reflectance resonance at a given frequency. Moreover, because of the dispersionless dielectrics, OPT can occur at multiple zero-reflectance resonance frequencies in a broad transmission band. The broadband OPT can be flexibly designed at various frequency ranges. As a proof of concept, we fabricate a twisted structure and experimentally demonstrate broadband OPT in the microwave range. Our work not only explores a physical method to realize broadband OPT in a low-loss and feasible platform but also has many potential applications in optical systems and photonic devices.