Detection of degenerate Stokes index states

Abstract

Stokes phase is the phase difference between orthogonal component states in the decomposition of any polarization state. Phase singularities in the Stokes phase distribution are Stokes singularities of an inhomogeneous polarization distribution. Under circular decomposition, Stokes phase distribution $$(\phi _{12})$$ ( ϕ 12 ) represents polarization azimuth $$(\gamma )$$ ( γ ) distribution and the singularities present in it are polarization singularities. Therefore, the charge of the Stokes vortices depicted as Stokes index $$\sigma _{12}$$ σ 12 is an important parameter associated with the polarization singularity. The Hybrid order Poincaré sphere (HyOPS)/Higher order Poincaré sphere (HOPS) beams, all having same Stokes index, contain a Stokes singularity at the center of the beam as these beams are constructed by vortex superposition. These beams, being superposition of orthogonal orbital angular momentum (OAM) states in orthogonal spin angular momentum (SAM) states can offer great multiplexing capabilities in communication. In this article, we identify these degenerate Stokes index states and discuss the ways and means of lifting this degeneracy. Otherwise, there are limitations on intensity based detection techniques, where demultiplexing or segregation of different HOPS/HyOPS beams is warranted. The method adduced here uses the diffraction of these beams through an equilateral triangular aperture in combination with polarization transformation as a probe to lift the Stokes index/Stokes phase degeneracy. Successively, the novelty of the detection scheme is discussed in the context of beams with alike polarization distributions where even the technique of Stokes polarimetry fails to predict the OAM and SAM content of the beam.

Production of orbital angular momentum states of optical vortex beams using a vortex half-wave retarder with double-pass configuration

“…Nevertheless, to identify the OAMs with diffraction patterns, the propagation of has to be involved 5 . According to our previous report 31 , we have applied adjustable combination gratings ( and in Fig.…”

“…Characteristics of circularly polarized vortex beams were examined by adopting the decomposition of cylindrical bases 3 and a special polarization grating 4 . Degenerate Stokes states were differentiated by a method associated with transformations of diffraction and polarization 5 . Additionally, studies on OAM light beams have shown promising applications in various fields.…”

Influence of High-Order Twisting Phases on Polarization States and Optical Angular Momentum of a Vector Light Field

“…Polarization conversions between linear and circular, and the manipulation of optical angular momentum in structured light fields are essential topics in optical field manipulation, with significant fundamental research interest and practical applications. The spin angular momentum (SAM) relies on circular polarization [27][28][29] (referred to as the S 3 in Figure 4), while the OAM is related to the gradient phase distribution [30]. The SAM and OAM densities of structured beams in the focal region can be calculated as follows:…”

Human psychophysical discrimination of spatially dependant Pancharatnam–Berry phases in optical spin-orbit states

“…Due to their unique propagation properties spin-orbit beams have found numerous applications in high-resolution imaging, communication protocols, and optical metrology 27 – 29 and a wealth of characterization techniques based on Stokes polarimetry have been developed 30 – 32 . Ref.…”