Dynamics of microparticles trapped in a perfect vortex beam

Abstract

We analyze microparticle dynamics within a "perfect" vortex beam. In contrast to other vortex fields, for any given integer value of the topological charge, a "perfect" vortex beam has the same annular intensity profile with fixed radius of peak intensity. For a given topological charge, the field possesses a well-defined orbital angular momentum density at each point in space, invariant with respect to azimuthal position. We experimentally create a perfect vortex and correct the field in situ, to trap and set in motion trapped microscopic particles. For a given topological charge, a single trapped particle exhibits the same local angular velocity moving in such a field independent of its azimuthal position. We also investigate particle dynamics in "perfect" vortex beams of fractional topological charge. This light field may be applied for novel studies in optical trapping of particles, atoms, and quantum gases.

Efficient generation of a perfect optical vortex by using a phase optical element

“…In [1], POVs are generated by using a phase optical element consisting of a set of concentric rings, the thickness of each of which approximates the delta function. In [2], POVs are generated by using a conical axicon and a spiral phase plate (SPP). In both works, the POV is generated approximately and its quality turned out to be low.…”

“…The element in [4] is closest to the optimal phase filter proposed in our work. Generation of POV is compared by using 1) an amplitude-phase light field described by a Bessel mode of limited radius, 2) by an optimal phase light field, described in [5] and 3) by the phase field generated by using a conical axicon and SPP [2].…”

“…The POV is often generated by using a conical axicon and a SPP [2]. When light passes through such setup, it is equivalent to passing an element with the following transmittance function:…”

“…Instead of scaling factor of the Bessel function, here the parameter  determines an axicon parameter, related with the vertex-angle of the generated conical wave. It is supposed in [2] that in the focus of a spherical lens the light field (5) generates a POV with its amplitude distribution described by the function…”

Photonic orbital angular momentum in starlight

“…Since the discovery by Allen et al (1992) that POAM can be easily created in the laboratory, it has been found in virtually every field of optics Yao & Padgett (2011);Tamburini et al (2012); Shalaev et al (2013); Kim et al (2013); Chen et al (2013) ;Cristi & Axtell (2013); Sun et al (2013); Ruane & Swatzlander (2013); Roux (2013); this ubiquity is evident in the more than 1000 papers citing the original work (Allen et al 1992). The demonstration that POAM is a natural consequence of the interaction of light and turbulence (Sanchez & Oesch 2011a,b;Oesch et al 2013), provides a mechanism by which POAM may be created in large quantities by astrophysical systems.…”