Zero-order and higher-order Bessel beams are well-known nondiffracting beams. Namely, they propagate with invariant profile (intensity) and carry a fixed orbital angular momentum. Here, we propose and experimentally study an anomalous Bessel vortex beam. Unlike the traditional Bessel beams, the anomalous Bessel vortex beam carries decreasing orbital angular momentum along the propagation axis in free space. In other words, the local topological charge is inversely proportional to the propagation distance. Both the intensity and phase patterns of the generated beams are measured experimentally, and the experimental results agree well with the simulations. We demonstrate an easy way to modulate the beam’s topological charge to be an arbitrary value, both integer and fractional, within a continuous range. The simplicity of this geometry encourages its applications in optical trapping and quantum information, and the like.
We propose a protocol for generating high-quality, partially coherent (quasi-)Bessel beam arrays with controllable beam order and spatial distributions. Our protocol involves, apart from beam intensity shaping, coherence engineering of recently introduced optical coherence lattices. Our theoretical results are validated with the experimental realization of partially coherent Bessel beam arrays. The novel beam arrays are anticipated to be useful for multi-particle trapping and micromanipulation, optical metrology and microscopy, as well as for 3D imaging.
We introduce an optical system for the nearly real-time generation of a wide class of partially coherent sources (PCSs) having non-Schell-model circular coherence. The system is composed of a modified 4f optical imaging system involving a fast modulated digital micro-mirror device (DMD) and a stable common path interferometric arrangement, which enable us to synthesize a variety of PCSs not reported heretofore. The basic principle and physics of our method, as well as the experimental implementation for generating two kinds of non-uniformly correlated (NUC) sources, i.e., cosh-type and sinh-type NUC sources, are presented, confirming the flexibility and reliability of our proposed approach. We further demonstrate the non-uniform property of the spatial correlation of the generated NUC sources by means of a classic Young's interferometer.
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