Superposition of vortex beams generated by polarization conversion in uniaxial crystals

Abstract

An optical system comprising a c-cut uniaxial crystal positioned between two axicons and illuminated by a Gaussian or a Laguerre–Gauss mode was used to demonstrate the generation of various vector vortex beams. We focused the generated beams using a 1 m focal length lens and we investigated their intensity profile and the polarization state in the focal plane of the focusing element. We showed that the achieved intensity profile can be controlled by changing the polarization state of the beam incident on the crystal. We observed that, for a particular configuration of the system, the initial circular symmetry of the beam is no longer preserved. The experiments were performed with Ti:Sapphire lasers that were operated in continuous wave mode, as well as in pulsed regime. The optical system presented here ensures a convenient way to generate a great variety of vector vortex beams and it is expected to be of interest for applications that use low and high-power laser sources, such as STED microscopy, light trapping, or material processing.

Gyrotropic Crystals as a Basis for Creation of Helical Polychromatic Singular Beams

“…The above Matrix (18) describes the transformation of the polarization state of a beam propagating in a gyrotropic crystal. A linearly polarized Gaussian beam passing through a crystal undergoes structural changes.…”

“…On the C-line, the field intensity, in the general case, does not vanish. The authors of [15][16][17][18][19] distinguish, in the form of characteristic features of the vector field, the so-called L-surfaces. On this surface, only linear polarization of partial waves exists.…”

“…Thus, the overall picture of the vector field after a uniaxial crystal is presented as a set of C and L-surfaces nested into each other, which cover the central C-line. Such a difference in the classification introduced in [15][16][17][18][19] with the vector field we are studying after a uniaxial crystal is due to the fact that in these works, the structure of random stochastic fields, which arises as a result of laser beam scattering on random anisotropic inhomogeneities, is studied.…”

“…It should be noted that the studies [16][17][18] are devoted to the study of the structure of polarization features in low-order Laguerre-Gauss beams that arise after excitation of the crystal by linearly polarized light. The authors of these papers focused on linearly polarized beams.…”

Fine Structure of Optical Vortices in Linearly Polarized Laguerre–Gaussian Beams in Oblique Beams Propagating a Uniaxial Crystal

“…It should be noted that studies [16][17][18] are devoted to the study of the structure of polarization singularities in low-order Laguerre-Gauss beams that arise after excitation of a crystal by linearly polarized light. The authors of these papers focused on linearly polarized beams.…”