Practical application of optical vortex in a method of three-dimensional profilometry with nanoscale resolution was considered. It was shown that phase analysis of coherent light beam carrying axial optical vortex allow to retrieve information about sample surface relief. High spatial resolution caused by vortex helical phase sensitivity to disturbances in wave front after reflection or spreading through studying sample, which can be optically transparent or have a reflecting surface. This method applicable for non-destructive testing of live cells and biological tissues in real-time regime with exceeding optical diffraction limit. Computer processing of vortex interferograms allow to achieve a vertical resolution down to 1.75 nm. Specially designed optical scheme reduces an environment influence, in particular, vibration, misalignment of test sample and its local anisotropy and provides the possibility of investigating surfaces of large linear dimensions. The prospective tasks of automated systems creation for monitoring of surface quality were proposed, in particular those that will could be developed with methods based on singular optics and phase singularities.
We have experimentally analyzed the behavior of Gaussian beam with elliptical cross-section passed through the uniaxial crystal in direction near perpendicular to the crystal’s optical axis. The projection of total angular momentum flux on the axis consists of projection of two components: the spin (SAM) and orbital (OAM) angular momentum. We have revealed that in anisotropic media the SAM describes the polarization state of the beam cross-section and OAM reflects the shape and topological charge of the singularity at ordinary and extraordinary beams. The sum of projections SAM and OAM remains constant. The oscillations of spin-orbital angular momentum projection were described experimentally during the crystal was rotated around z axis with small beam inclination. The low changes in the extraordinary beam cross section and their correlation with polarization state allow us to analyze the form of angular momentum conversion and possibility for generation of polarizing singularities. The feasibility of optical vortex generation in the system of uniaxial crystal with tilted Gaussian beam was theoretically and experimentally investigated.
In this paper we report on the progress in building the superresolution microscope using optical vortices. The outline of the general idea is presented. Some of the specific problems are discussed in more details. Specifically, the scanning
method by vortex lens movement is discussed.
We have experimentally analyzed the topological reactions occurred in the elliptic vortex-beam transmitting
orthogonally to the optical axis of the SiO2 crystal. We have revealed that the oscillations of the polarization state when
propagating the beam are accompanied by reconstruction of the polarization singularities at the beam cross-section that, in
turn, entails the reconstruction of the wavefront in each circularly polarized beam component. Both synchronic oscillations of
the spin angular momentum and the sign of the vortex topological charge are expressing in a field structure as birth and
annihilation of topological dipoles. Also periodical conversion of the vortex ellipticity along the crystal length z and huge
splash of spin angular momentum were analysed. The run of the dislocation reactions in the beam component results in
converting the sign of the topological charge in the centered optical vortex, the distance of the vortex conversion being about
0.05 of the wavelength.