Scalar topological photonic nested meta-crystals and skyrmion surface states in the light cone continuum

Topological photonics is rapidly expanding. However, discovering three-dimensional topological electromagnetic systems can be more challenging than electronic systems for two reasons. First, the vectorial nature of electromagnetic waves results in complicated band dispersions, and simple tight-binding-type predictions usually fail. Second, topological electromagnetic surface modes inside the light cone have very low quality factors (Q factors). Here, we propose the concept of scalar topological photonics to address these challenges. Our approach is experimentally validated by employing a nested meta-crystal configuration using connected coaxial waveguides. They exhibit scalar-wave-like band dispersions, making the search for photonic topological phases an easier task. Their surface states have skyrmion-like electric field distributions, resulting in a whole, bright surface state band inside the light cone continuum. As such, the topological surface states in our three-dimensional nested crystals can be exposed to air, making such systems well-suited for practical applications. Employing connected coaxial waveguides on a nested meta-crystal configuration, the authors design photonic crystals with scalar-wave-like band dispersions, facilitating the search for topological phases in three-dimensional photonic crystals.

Automated summary

We propose the concept of scalar topological photonics and experimentally validate it by employing a nested meta-crystal configuration using connected coaxial waveguides. This approach exhibits scalar-wave-like band dispersions, making the search for photonic topological phases easier and the surface states can be exposed to air, making it well-suited for practical applications.