Obstruction immune topological propagation in 3D-printed metal-based photonic crystals

Abstract

Topological photonic systems have recently become an important platform for manipulating the flow of electromagnetic (EM) waves owing to unique features like backscattering-immune unidirectional propagation of light which could be harnessed for various robust-device applications. In this context, recent advances in 3D printing have further facilitated the practical implementation of a variety of topological systems offering enormous flexibility in designing the devices. With this pretext, we experimentally demonstrate a 3D-printed topological photonic crystal (TPC) constituted by cylindrical metal rods, wherein topological propagation is enabled through a zigzag-type domain boundary (DB) formed by merging two valley photonic crystals. The valley edge mode generation as well as the robust propagation of EM waves in the TPC sample are probed in the presence of different physical obstacles in the form of dielectric and metallic blocks. Very high transmission with an approximate minimal loss of ∼−1.3 dB to −3.8 dB is observed even in the presence of obstacles in the DB. The strong EM field confinement across the DB is further validated through experimentally capturing the electric field distributions in the xy-plane of the studied TPC. The demonstrated TPC scheme can open new routes towards the development of cost-effective devices requiring robust EM transmission even in the presence of foreign obstacles/defects.