Abstract
In this paper, we characterize the helical beam structure through an analysis of the spiral character of the phase distribution inside a light beam. In particular, we show that a line connected with the 2π phase jump in the Laguerre–Gauss beam can be described by a Fermat’s spiral. We propose a numerical fitting method to determine the parameters of a spiral equation for the phase distribution of the helical beam. Next, we extend the procedure to a vortex beam created by the spiral phase plate and apply it to experimental phase maps, which allows us to recover the phase shift introduced into the object beam in the optical vortex scanning microscope.
Highlights
Structured light with non-Gaussian intensity profiles and with spatially variant phase distributions is getting attention in many fields of optical science and technology
We propose a procedure for recovering parameters of the spiral from the phase map. We show that this concept of beam description can be applied in the case of a helical beam created by the spiral phase plate which is used in the optical vortex scanning microscope [10,11]
In the experimental part, which is described the vortex beam is generated by the spiral phase plate (SPP)
Summary
Structured light with non-Gaussian intensity profiles and with spatially variant phase distributions is getting attention in many fields of optical science and technology. One can observe a dark area (the vortex core) surrounded by a bright ring [4] Another unique aspect of this beam is the phase distribution. We propose a new way for characterizing a vortex beam through the analysis of its phase distribution contour. We show that this concept of beam description can be applied in the case of a helical beam created by the spiral phase plate which is used in the optical vortex scanning microscope [10,11]. We apply this new way of beam description to recover the phase shift introduced into the object beam in the optical vortex scanning microscope.
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