An on-chip chiral converter and polarization rotator

Abstract

An on-chip half-wave plate (HWP) based on pure dielectric waveguides, which is capable of switching the handedness of a quasi-circularly polarized mode or rotating the polarization of a quasi-linearly polarized mode, is proposed and demonstrated. The concept of birefringence is used to give rise to a phase retardance of π between two orthogonally polarized modes in nanophotonic waveguides. Remarkably, the proposed component is compact (4.66 μm) with a high energy conversion efficiency (more than 98 %) and an ultra-wide operation band of about 130 nm around the telecom wavelength λ = 1.55 μm. We expect our results to have new perspectives for polarization handling in nanophotonic silicon waveguides, and they may find important applications in many optical systems with limited physical space, such as integrated quantum information processing and nano-optical manipulation.