Topological Edge Mode Tapering
Christopher J. Flower, Sabyasachi Barik, Mahmoud Jalali Mehrabad, Nicholas J. Martin, Sunil Mittal, Mohammad Hafezi
Abstract
Mode tapering, or the gradual manipulation of the size of some mode, is a requirement for any system that aims to efficiently interface two or more subsystems of different mode sizes. While high-efficiency tapers have been demonstrated, they often come at the cost of a large device footprint or challenging fabrication due to backscattering or excitation of higher-order modes. Topological photonics, offering robustness to certain types of disorder as well as chirality, has proved to be a well-suited design principle for numerous applications in recent years. Here we present a new kind of mode taper realized through topological band gap engineering. We numerically demonstrate a 6-fold change in mode width over an extremely compact 8 μm distance with near unity efficiency in the optical domain. With suppressed backscattering and no excitation of higher-order modes, such a taper could enable new progress in the development of scalable, multicomponent systems in classical and quantum optics.