ACS Nano https://doi.org/ch7x (2018)
One promising way of controlling light waves is by topologically structuring laser beams with vortices. A helical wavefront and a central phase singularity then make the light amenable to ultrahigh-resolution microscopy, and its optical angular momentum can be used to store and transfer information — offering scope for holographic applications and 3D displays. But existing implementations operate in the unfavourable infrared frequency range and claim limited control over the angular momentum. Now, Thomas Krauss and co-workers have developed an integrated approach that provides access to miniaturization and a facile scaling.
Krauss et al. realized an organic semiconductor laser emitting in the visible frequency range with a controllable optical vortex. The key element is an Archimedean spiral grating, which gives access to the phase, handedness and angular momentum of the beam through the number of spiral arms. This effectively transfers the concept of optical vortices to the microscale and makes it possible to construct two-dimensional arrays of cheap, easy-to-fabricate and spectrally tunable emitters in a single lightweight device.
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Kraack, J. Scalable vortices. Nature Phys 14, 108 (2018). https://doi.org/10.1038/nphys4355