Spin–orbit photonic diode from biomimetic 3D chiral liquid crystal architectures

Abstract

Spin–orbit photonic devices usually rely on 2D (transverse) material structuring and are designed for optimal coupling between the polarization state and the spatial degrees of freedom at a given wavelength. Exploiting the third dimension (longitudinal) provides ways to bypass monochromatic limitations. Within a singular optics framework, here we show that chiral liquid crystals endowed with non-singular 3D helix axis orientational distribution exhibit transmissive broadband spin–orbit optical vortex generation as well as an optical diode effect. These results are in stark contrast to the properties of spin–orbit optical elements fabricated from chiral liquid crystals with a uniform orientation of the helix axis, which are reflective devices that process forward and backward propagating waves equally. Moreover, the similarities between the proposed 3D chiral structure and that of the cuticle of some insects invites considering spin–orbit photonics from a biological perspective.