Spiral relief formation in an azo-polymer film by the irradiation of a circularly polarized optical vortex beam

摘要

Optical vortices with a helical wavefront due to a phase singularity, and circularly polarized light with a helical electric field have an orbital angular momentum (Lħ) and a spin angular momentum (Sħ), respectively. Consequently, a circularly polarized optical vortex will carry the total angular momentum (Jħ=Lħ+Sħ), defined by the vector sum of the orbital and spin angular momenta. In recent years, we and our-coworkers discovered an interesting phenomenon, in which the angular momentum of the optical vortex is transferred to an irradiated metal target through an ablation process, providing twisted nanoneedles [1,2].