Vortex beam is produced by spiral phase plate in STED microscopy, for example. What is the nature of its polarization? radial? azimuth? or mixed of both (spiral)? does it depend on input polarization?. Can linearly polarized vortex beam exist as center is always zero?
Thanks
Mahendar
In principle the polarisation structure of a beam can be set independently of the spatial structure of the intensity. For example if a linearly polarised Gaussian beam illuminates a forked diffraction grating then the results vortex beam (in the first diffractive order) is still linearly polarised. For example, the beams made by Marat Soskin and other. These beams can be described as scalar beams where at every position in the beam one can express both a complex amplitude and a polarisation state.
Alternatively one can create "vector" beams where the polarisation structure itself maps to the field. Eg a radially polarised beam with a zero on-axis intensity. For example, the beams made by Gerd Leuchs and others.
Hi John,
Thank you very much for answer. I have a partial knowledge on these vector and scalar vortex beams. If I use spiral phase plate to generate vortex beam, I read in one publication (link given) that it creates vortex beam with spiral polarization. This spiral polarization is roughly linear combination of radial and azimuth and it is regarded as scalar beam.
http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-31-7-867
can you please suggest me any article or lecture on vector and scalar vortex beams?
just to add something, I have watched your sort video on these optical vortices on spie TV. It has given over view of optical vortices for non-experts of optics. Thanks for that.
Thanks for your time
Mahendar
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