Abstract

An optical beam with a helical phase is characterised by an /l/ start (alternatively /l/ charge) helical wave front as produces by e.g. a spiral zone plate or a holographic element. Helical wave fronts also occur in Laguerre-Gaussian beams and higher order Bessel beams. The helical wave carries angular momentum and on propagation produces optical vortices. Photon spin (due to circular polarisation) and optical angular momentum (helical waves) will be briefly discussed. Applications to be considered include (a) the trapping and rotation of particles, (b) modification of the shape of the dark vortex core to guide particles into required patterns and assemblies, (c) fractal zone plates for producing a sequence of focused and structured optical vortices along the propagation direction (d) the self-reconstructive properties of integer and fractional Bessel beams and special applications of the latter, (e) variations in optical angular momentum to encode data of different charges for secure free-space optical transmission.

• Work in collaboration with my previous PhD student, Professor Xiaocong Yuan, and his colleagues. Professor Yuan is soon to be appointed to a Chair of Optical Engineering in Nankai University, Tianjin, China.