Generation of Higher-Order Optical Angular Momentum Beams using In-Fibre Mode Converter and Spiral Phase Plate

Optical angular momentum (OAM), also known as vortex beams (VB), are characterised by the spatial distribution of their electric field, which exhibits a spiral variation around the axis of propagation and a phase singularity at their centre, resulting in a discontinuity that gives rise to their unique doughnut-shaped intensity profile. The pioneering work in [1] triggered significant research progress into OAM beams and has been used in many fields since. Applications include optical tweezers and micromanipulation, quantum optical communications, and even materials processing. For example, a proof of principle experiment demonstrated the ability of vortex beams to machine nanoscale needles [2], highlighting their potential in precision nanofabrication.