Miniature chiral beamsplitter based on gyroid photonic crystals

The linearly polarizing beamsplitter 1 , 2 is a widely used optical component in photonics. It is typically built from a linearly birefringent crystal such as calcite, which has different critical reflection angles for s - and p -polarized light 3 , leading to the transmission of one linear polarization and angled reflection of the other. However, the analogue for splitting circularly polarized light has yet to be demonstrated due to a lack of natural materials with sufficient circular birefringence. Here, we present a nano-engineered photonic-crystal chiral beamsplitter that fulfils this task. It consists of a prism featuring a nanoscale chiral gyroid network 4 , 5 , 6 , 7 , 8 , 9 , 10 and can separate left- and right-handed circularly polarized light in the wavelength region around 1.615 µm. The structure is fabricated using a galvo-dithered direct laser writing method and could become a useful component for developing integrated photonic circuits that provide a new form of polarization control. A chip-compatible beamsplitter that can separate left- and right-handed circularly polarized light is promising for constructing more sophisticated integrated optical circuits. The prism-shaped device, which operates around the telecommunication wavelength of 1.5 μm, consists of a photonic crystal composed of an array of helical structures.