Propagation of vortex beams through self-assembled photonic crystal

This study describes a new and simple approach to produce multiple optical vortices (OVs) using three-dimensional polymeric photonic crystal (PhC). The crystals are fabricated by well-known inward-growing self-assembly technique using polystyrene micro-particles of particle sizes 990 and 1900 nm. This fabrication technique provides the cubic lattice arrangement to the spheres with the ⟨1 1 1⟩ plane parallel to the substrate. When a Gaussian beam from a He–Ne laser at 633 nm is diffracted through the crystal of particle size 990 nm, six bright spots along with a central spot are observed on the screen. Diffractions are observed up to third-order in the case of 1900 nm particle size PhC. Multiple OVs arise when vortex beam with topological charge 1 is diffracted through such a crystal. The diffraction pattern shows similar arrangement of bright spots as for the Gaussian beam except now the diffracted spots contain the property of incident OV, i.e. the central dark core. The diffraction is recorded using a charge coupling device camera.