Broadband chiral silicon photonic circuits based on fork-type inversely tapered nanowire waveguides

Optical spin or circular polarization provides a new degree of freedom to control light-matter interaction in the fundamentals and applications of light. To broaden the bandwidth of chiral (spin-controlled) coupling in photonic integrated circuits, we propose fork-type inversely tapered nanowire waveguides to compensate for the out-of-step phase evolution of adiabatic coupling between TE0 and TM0 (TE1) modes excited from the x- and y-polarization components of spin polarized light in free space, respectively. We design and simulate two kinds of devices based on air and Si3N4 up-claddings to show the feasibility of broadening the bandwidth of chiral silicon photonic circuits by using fork-type inverse tapers. Numerical results show that the bandwidth can approach 70 nm under high directionality of above 0.90. This broadband chiral coupling via the new phase synchronizing technique with fork-type inverse tapers may pave the way to develop on-chip spin photonics or polarization based photonic integrated devices. (C) 2021 Optical Society of America

Automated summary

This paper proposes a method to broaden the bandwidth of chiral coupling using fork-type inversely tapered nanowire waveguides, and designs and simulates two device models based on different cladding materials to demonstrate the feasibility of this approach, achieving a bandwidth of 70 nm under high directionality.