Generation of Stokes singularities using polarization lateral shear interferometer

Abstract

Lateral shear interferometer, being a self-referenced interferometer, has proven to be an important tool in scalar optics. Here we employ a vectorial counterpart - polarization lateral shear interferometer, in which the two interfering beams apart from being derived from the test wavefront, are in orthogonal states of polarization. Therefore when the test wavefront has spatially varying phase gradient across the beam cross-section, the resulting shearogram produces polarization fringes instead of intensity fringes. Further, the shearogram becomes inhomogeneously polarized. This polarization lateral shear interferometer may have potential uses in metrology, but in this article we demonstrate the ability of the interferometer in the generation of all Stokes singularities in the single beam by launching a phase singular beam into it. It is found that a vortex dipole is formed along with other generic Stokes singularities. Experimental observations support the results and they are discussed in the article.

Self-referenced interferometry for single-shot detection of vector-vortex beams

“…The optical field can hold vortices in many other forms. For example, laser beams can hold engineered phase and polarization singularity distributions as composite vortices 64 – 66 . They can hold multiple singularity points.…”

Manipulation of polarization topology using a Fabry-Pérot fiber cavity with a higher-order mode optical nanofiber

“…Singularities of 𝜎 12 are known as V-points and C-points, in vector and ellipse fields, respectively [42]. Singularities of 𝜎 23 and 𝜎 31 are known as Poincaré vortices [43][44][45]. L-lines are located where 𝜙 23 = {0, 𝜋, 2𝜋}.…”

“…In recent years, complex polarization distributions and the generation of polarization singularities have been investigated using various methods, giving rise to the relatively new field of singular optics [41]. Polarization singularities are a subset of Stokes singularities, i.e., phase singularity points in Stokes phases [42,43]. In fact, higher-order fiber eigenmodes are vector optical fields with a polarization singularity called a V-point, where the state of polarization (SOP), i.e., how the polarization is distributed in the cross-section of a given mode, is undefined [41].…”

“…In fact, higher-order fiber eigenmodes are vector optical fields with a polarization singularity called a V-point, where the state of polarization (SOP), i.e., how the polarization is distributed in the cross-section of a given mode, is undefined [41]. Other types of Stokes singularities can be formed in elliptical optical fields, such as the polarization singularity of C-points, where the polarization orientation is undefined [41,42], and Poincaré vortices, where the polarization handedness is undefined [43][44][45]. Moreover, points of linear polarization can form continuous lines, which are classified as L-lines [41].…”

“…The generation of all Stokes singularities within a single beam has been demonstrated using a free-space interferometer [43,46]. Modal interference in a birefringent crystal can facilitate the creation of polarization singularities [47,48].…”