I. V. Izmailov

Wave and Ray Spatial Dynamics of the Light Field in the Generation, Evolution, and Annihilation of Phase Dislocations

The spatial dynamics of the light field during the generation, evolution, and annihilation of screw phase dislocations in Gaussian optical beams is analyzed. The regularities of transformation of an aberration wave front of a beam into a singular front are exposed. The structure of the field of directions of the energy-flux density vector is analyzed on the basis of a solution of a parabolic wave equation for the complex amplitude of a monochromatic light field with the construction of streamlines and investigation of the full set of critical points in the corresponding dynamic system. It is established that the energy redistribution in the beam and appearance of dislocations occur in accordance with the transformation of singularities: local focusing of a streamline in the vicinity of a node is a precursor of a generated pair of screw dislocations, and the streamline takes on a helix shape near an unstable focus.

Correction of vortex laser beams in a closed-loop adaptive system with bimorph mirror

The sensing of phase front of the vortex laser beams has been carried out with the help of a Hartmann-Shack sensor. The vortex beam is generated in the form of a Laguerre-Gaussian beam (LG0 1 mode) with the help of the special helicoidal phase plates manufactured by the kinoform technology. The measured shifts of focal spots on the hartmannogram are compared with the calculated shifts. From the measured wave front tilts the reconstruction of singular phase surface has been performed with using the novel reconstruction technique. The phase surface reconstruction is demonstrated in the case of distorted vortices as well. The correction of an optical vortex is undertaken in the close-loop adaptive system including the bimorph deformable piezoceramics-based mirror.

Wave front sensing of an optical vortex and its correction in the close-loop adaptive system with bimorph mirror

The sensing of phase front of the vortex laser beam has been carried out with the help of a Hartmann-Shack sensor. The vortex beam is generated in the form of a Laguerre-Gaussian beam (LG01 mode) with the help of the special helicoidal phase plates manufactured by the kinoform technology. The measured shifts of focal spots on the hartmannogram are compared with the calculated shifts. From the measured wave front tilts the reconstruction of singular phase surface has been performed with using the novel reconstruction technique. The removing of phase singularity from an optical vortex is demonstrated in the close-loop adaptive system including the bimorph deformable piezoceramics-based mirror.

Singular wavefront reconstruction with the tilts measured by Shack-Hartmann sensor

In the present report the possibility of singular points detections using a Shack-Hartmann sensor is described and the precision of the developed detection algorithm is estimated. Also the algorithms of a singular wave front reconstruction are analyzed. Two algorithms are considered and their properties compared. One of them was developed by D. Fried, its description was found in literature. The second algorithm was developed by authors of the report. The both algorithms were introduced into the software of the sensor and insured satisfactory quality of singular phase reconstruction. The precision of algorithms compared in numerical investigations as well in real laboratory experiments.

Performance of a wavefront sensor in the presence of singular points

In the present report the possibility of singular points detections using a Shack-Hartmann sensor is described and the precision of the developed detection algorithm is estimated. Also the algorithms of a singular wave front reconstruction are analyzed. Two algorithms are considered and their properties compared. One of them was developed by D. Fried, its description was found in literature. The second algorithm was developed by authors of the report. The both algorithms were introduced into the software of the sensor and insured satisfactory quality of singular phase reconstruction. The precision of algorithms compared in numerical investigations as well in real laboratory experiments.

Localization of optical vortices and reconstruction of wavefront with screw dislocations

A new algorithm of the dislocation localization is suggested. It is based on the analysis of projections field of phase gradients. Accuracy of the algorithm is verified by numerical simulation. Special attention is focused on the precision of singular points (wavefront dislocations) screening. The algorithm is evaluated with respect to others and its advantages and drawbacks are cleared up. The method described can be included in the software of the Hartmanns sensor and be used in the full-scale experiments. Also the original algorithm of phase reconstruction is proposed and its characteristics are estimated. This algorithm requires detection of dislocation coordinates so it should be used together with the algorithm of dislocation localization. In the paper the comparison is performed of the proposed algorithm with the well known Frieds algorithm. After that the phase reconstruction technique is included into the model of a typical adaptive optics system.

Algorithms of a singular wavefront reconstruction

The original algorithm of phase reconstruction is proposed and its characteristics are estimated. This algorithm requires detection of dislocation coordinates so it should be used together with the algorithm of dislocation localization. In the paper the comparison is performed of the proposed algorithm with the well known Frieds algorithm. After that the phase reconstruction technique is included into the model of a typical adaptive optics system.

Deterministic Chaos Phenomenon from the Standpoint of Information Protection Tasks

Elements of classical cryptology are described. The optical vortex is interpreted as the information carrier. Fundamentals of the dynamic chaos oscillator operation are disclosed including optical ones, mathematical models are discussed, principles of its application for information protection are described.

Dynamic chaos in a problem of objects positioning: On a capability and features of application

Possibility of dynamic chaos using for determination of navigation objects position (over a communication channel length, or for a signal delay time in it) is discussed. In this context the correlation properties of dynamic modes of spiral and screw chaos types are studied and compared using a Rössler generator as an example:.

Registration of vortex beam parameters in a turbulent atmosphere

In this paper detection of vortex beam parameters in a turbulent atmosphere is considered numerically. The characteristics of singular radiation were obtained with the use of wavefront gradients, i.e. an ideal system was simulated. After that, a model of a Shack–Hartmann sensor was included in the calculation schematic which allowed us to assess the influence of the device limitations on the precision of registration and optimize its parameters.