X-type vortex and its effect on beam shaping

TL;DR

This paper introduces the X-type optical vortex, a novel vortex with unique focusing and beam shaping properties, enabling controllable 3D beam patterns and phenomena like the 'switch effect' for advanced optical field manipulation.

Contribution

The paper proposes the X-type vortex, a new vortex type with non-constant phase gradient, and analyzes its unique focusing properties and applications in 3D beam shaping.

Findings

Demonstrates controllable beam patterns from doughnut to lobed shapes.

Observes the 'switch effect' enabling intensity pattern shifts in focal plane.

Shows twisting 3D beam structures with controllable rotation.

Abstract

In this article we propose a new type of optical vortex, the X-type vortex. This vortex inherits and develops the conventional noncanonical vortex, i.e., it no longer has a constant phase gradient around the center, while the intensity keeps invariant azimuthally. The strongly focusing properties of the X-type vortex and its effect on the beam shaping in three-dimensional (3D) fields are analyzed. The interesting phenomena, which cannot be seen in canonical vortices, are observed, for instance the 'switch effect' which shows that the intensity pattern can switch from one transverse axis to another in the focal plane by controlling the phase gradient parameter. It is shown that by adjusting the phase gradient of this vortex, the focal field can have marvelous patterns, from the doughnut shape to the shapes with different lobes, and the beam along propagation direction will form a twisting shape in 3D space with controllable rotation direction and location. The physical mechanisms underlying the rule of the beam shaping are also discussed, which generally say that the phase gradient of the X-type vortex, the orbital angular momentum, the polarization and the 'nongeneric' characteristic contribute differently in shaping fields. This new type of vortex may supply a new freedom for tailoring 3D optical fields, and our work will pave a way for exploration of new vortices and their applications.