Abstract
Structured light with more controllable degrees-of-freedom (DoFs) is an exciting topic with versatile applications. In contrast to conventional vector vortex beams (VVBs) with two DoFs of orbital angular momentum (OAM) and polarization, a hybrid ray-wave structure was recently proposed [Optica 7(7), 820-831 (2020)], which simultaneously manifests multiple DoFs such as ray trajectory, coherent state phase, trajectory combination, besides OAM and polarization. Here we further generalize this exotic structure as the astigmatic hybrid VVB by hatching a new DoF of astigmatic degree. Importantly, the transverse topology varies with propagation, e.g. a linearly distributed hybrid trajectory pattern can topologically evolve to a circularly polygonal star shape, where the number of singularity changes from zero to multiple in a single beam. The propagation-dependent evolution can be easily controlled by the astigmatic degree, including as a vector vortex state such that different astigmatic trajectories have different polarizations. We experimentally generate such beams from a simple laser with a special astigmatic conversion by combined spherical and cylindrical lenses, and the results agree well with our theoretical simulation. With our new structured light, the propagation-multiplexing multi-DoF patterns can be controlled in a single beam, which can largely extend related applications such as high-dimensional large-capacity optical communication, laser machining, and particle trapping.
Highlights
Structured light has attracted increasingly attention for its diverse applications in both classical and quantum optics, taking advantage of its customized distribution of intensity, phase, polarization, orbital angular momentum (OAM), and other degrees-of-freedom (DoFs) [1,2,3]
In contrast to conventional vector vortex beams (VVBs) manipulated by two DoFs, i.e. OAM mode and polarization, the SU(2) geometric beam has recently demonstrated the capability of manipulating more DoFs due to its unique structure of ray-wave duality (RWD) [33,34,35,36,37], which can be described by both the geometric ray trajectories and coherent wave-packet
We propose a new kind of VVBs with astigmatic hybrid trajectory structure, which introduces a new DoF, i.e. the astigmatic degree, in hybrid SU(2) geometric beams
Summary
Structured light has attracted increasingly attention for its diverse applications in both classical and quantum optics, taking advantage of its customized distribution of intensity, phase, polarization, orbital angular momentum (OAM), and other degrees-of-freedom (DoFs) [1,2,3]. In contrast to conventional VVB manipulated by two DoFs, i.e. OAM mode and polarization, the SU(2) geometric beam has recently demonstrated the capability of manipulating more DoFs due to its unique structure of ray-wave duality (RWD) [33,34,35,36,37], which can be described by both the geometric ray trajectories and coherent wave-packet Such a geometric beam can be directly generated from a laser cavity when the cavity geometry is precisely controlled into a frequencydegenerate state that fulfills a periodic ray trajectory in laser oscillator [36,37,38,39]. The hybrid SU(2) VVB plays as an ideal candidate to meet the requirement of the development of multi-DoF structured light
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