Topologically Enabled On‐Chip THz Taper‐Free Waveguides

Abstract

AbstractWaveguide tapers are seemingly indispensable elements in silicon photonics that usually operate adiabatically to maximize the coupling efficiency between waveguides with different cross‐sections, which, however, necessitate large footprints. To date, great efforts have been made to minimize the tapers’ footprints while maintaining their efficiency. Contrary to conventional wisdom, here, a concept of taper‐free waveguides is proposed in which waveguides with different cross‐sections couple with each other efficiently without using tapers, which are enabled by the recently discovered photonic topological phases. This concept is experimentally demonstrated on an all‐silicon on‐chip terahertz (THz) wave platform. It is further shown that the topologically enabled taper‐free waveguides are robust against sharp corners and large‐area potential barriers. This work provides a promising taper‐free solution for future compact optical/THz photonic integrated circuits.