Daan Stellinga, Monika E. Pietrzyk, James M. E. Glackin, Yue Wang, Ashu K. Bansal, Graham A. Turnbull, Kishan Dholakia, Ifor D. W. Samuel, and Thomas F. Krauss
ASC Nano, 10.1021/acsnano.7b07703 (2018)
Optical vortex beams are at the heart of a number of novel research
directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturisation, a more integrated yet scalable method is highly desirable. Here, we demonstrate the generation of an azimuthally polarised vortex beam directly by an organic semiconductor laser that meets these requirements. The organic vortex laser uses a spiral grating as a feedback element that gives control over phase, handedness and degree of helicity of the emitted beam. We demonstrate vortex beams up to an azimuthal index l = 3 that can be readily multiplexed into an array configuration.