Variable-radius focused optical vortex with suppressed sidelobes

University of Cambridge, Cambridge, England, United Kingdom
Optics Letters (Impact Factor: 3.29). 07/2006; 31(11):1600-2. DOI: 10.1364/OL.31.001600
Source: PubMed


We propose a design for a phase mask for generating an optical vortex with suppressed sidelobes in the focal plane where the radius of the intensity ring is variable. A radial modulation added to conventional phase mask exp(iltheta) projects the light diffracted from different annular zones into a single intensity ring in the focal plane.

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    • "From the point of view of trapping efficiency it is desirable to provide a large value of parameter ν and a small value of parameter ρ 0 simultaneously. However, the known techniques for generating optical vortex beams exhibit a strong (almost linear) dependence between these two parameters [2] [3] [4]. Here we propose a new technique for generating the optical vortex beam free from this shortcoming and show how such vortex is approximately generated in the Fourier transforming optical system using a computer-controlled liquid crystal spatial light modulator (LC-SLM) placed at the object plane. "
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    ABSTRACT: A novel technique for vortex generation using the liquid crystal spatial light modulator is proposed. Unlike other methods, the vortex radius is chosen independently of the topological charge. Experimental results using LC2002 modulator are shown.
    Full-text · Conference Paper · Jan 2013
    • "As is known for an LG beam, the variation of intensity with radial coordinate on the exit pupil plane changes with the value of the Gaussian background size and the topological charge m. The radius of the primary ring in the diffraction pattern no longer scales with the topological charge and is determined by the radial modulation function and the topological charge together [44]. The intensity distribution also undergoes modification and the size of the focused vortex ring influences the transfer of orbital angular momentum to the trapped particles [45]. "
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    ABSTRACT: The effects of astigmatism and defocusing on the intensity distribution and encircled energy for a beam with an on-axis vortex embedded in a Gaussian background have been investigated using the Fresnel–Kirchhoff diffraction integral. A study has been carried out for two values of the topological charge for a truncated beam, and the stability of the optical vortices under the influence of aberration has been analysed. Some results are also presented for the influence of the truncation parameter of the beam. The aberration results in flattening of the dark core, and elongation of the core along a particular direction, thus resulting in a tail-shaped point spread function. Twofold symmetry is observed for selected defocused planes, and the diffraction pattern becomes more complex with an increase in the value of the aberration. The combined effect of astigmatism and coma on the PSF is also investigated.
    No preview · Article · May 2007 · Journal of Optics A Pure and Applied Optics
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    ABSTRACT: We present a new approach for generating an optical vortex pattern with reduced sidelobes without increasing the radius of the vortex and without excessive energy loss. Our technique combines the spiral phase plate with a weak axicon to form a helical axicon. Experimental results using a liquid crystal display agree with theory.
    Full-text · Article · May 2007 · Optics Letters
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