Hybrid Refractive–Diffractive Optical Vortex Microlens.

We report a novel hybrid refractive–diffractive microlens combined with spiral phase for the generation of optical vortex, which is fabricated via femtosecond laser direct writing technology. The unique optical performance of focusing capability is demonstrated. At the focus position, the hollow focus with different integer topological charges is investigated. Moreover, experimental results are supported by finite-element calculation. The novel microlens generating an optical vortex will fulfill important applications in optical manipulation, multistate information encoding, quantum communication, and computation, particularly in the compaction, integration, and simplification of optical vortex generation system. [ABSTRACT FROM PUBLISHER]