Roman I. Egorov

Topological networks of paraxial ellipse speckle-fields

Structural units of singular paraxial ellipse fields, and their self-organization to form complementary topological networks of azimuth and eccentricity, are considered. The recently established technique of singular Stokes polarimetry is described and its capabilities are discussed. The azimuthal and eccentricity networks of generic paraxial ellipse speckle-fields were measured for the first time. Statistics of structural units and extreme are defined and compared quantitatively with theoretical predictions. Their essential difference allows us to conclude that generated speckle-fields generally possess non-Gaussian statistics. Applications of singular Stokes polarimetry as a new tool for the comprehensive characterization of ellipse fields of arbitrary complexity are discussed and demonstrated.

Measurement of the morphological forms of polarization singularities and their statistical weights in optical vector fields

Using the developed optical method, elliptically polarized fields were taken as examples for the experimental measurement of all three possible morphological forms in the vicinities of the circular polarization points and of their statistical weights in generic speckle fields.

Singular Stokes-polarimetry as new technique for metrology and inspection of polarized speckle fields

Polarimetry is effective technique for polarized light fields characterization. It was shown recently that most full “finger-print” of light fields with arbitrary complexity is network of polarization singularities: C points with circular polarization and L lines with variable azimuth. The new singular Stokes-polarimetry was elaborated for such measurements. It allows define azimuth, eccentricity and handedness of elliptical vibrations in each pixel of receiving CCD camera in the range of mega-pixels. It is based on precise measurement of full set of Stokes parameters by the help of high quality analyzers and quarter-wave plates with λ/500 preciseness and 4’ adjustment. The matrices of obtained data are processed in PC by special programs to find positions of polarization singularities and other needed topological features. The developed SSP technique was proved successfully by measurements of topology of polarized speckle-fields produced by multimode “photonic-crystal” fibers, double side rubbed polymer films, biomedical samples. Each singularity is localized with preciseness up to ± 1 pixel in comparison with 500 pixels dimensions of typical speckle. It was confirmed that network of topological features appeared in polarized light field after its interaction with specimen under inspection is exact individual “passport” for its characterization. Therefore, SSP can be used for smart materials characterization. The presented data show that SSP technique is promising for local analysis of properties and defects of thin films, liquid crystal cells, optical elements, biological samples, etc. It is able discover heterogeneities and defects, which define essentially merits of specimens under inspection and can’t be checked by usual polarimetry methods. The detected extra high sensitivity of polarization singularities position and network to any changes of samples position and deformation opens quite new possibilities for sensing of deformations and displacement of checked elements in the sub-micron range.

Topological response of inhomogeneous, elliptically polarized, light fields to controlled anisotropic perturbations

The effect of controlled anisotropic losses on the topological structure of complex, elliptically polarized, light fields has been investigated. It has been shown that they can either initiate topological reactions with the appearance/disappearance of C points, saddle points, etc., or induce only their slight shift. Both strong and slight topological responses can be realized in the same field at sections with different inhomogeneity degrees of the polarization parameters of the field.

Conoscopic patterns in photonic band gap of cholesteric liquid crystal cells with twist defects

We investigate theoretically the effects of the angle of incidence on light transmission through cholesteric liquid crystals. The systems are two-layer sandwich structures with a twist defect created by rotation of the one layer about the helical axis. The conoscopic images and polarization-resolved patterns are obtained for thick layers by computing the intensity and the polarization parameters as a function of the incidence angles. In addition to the defect angle-induced rotation of the pictures as a whole, the rings associated with the defect mode resonances are found to shrink to a central point and disappear, as the defect twist angle varies from zero to its limiting value π/2 and beyond.