Anatol A. Ryzhevich

Propagation of high-order circularly polarized Bessel beams and vortex generation in uniaxial crystals

We investigate the generation and transformation of Bessel beams through linear and nonlinear optical crystals. We outline the gen- eration of high-order vortices due to propagation of Bessel beams along the optical axis of uniaxial crystals and expand this to the nonlinear regime by outlining a new phase-matching process (full conical phase matching) in second harmonic generation of vector Bessel beams for various sym- metries in uniaxial crystals. We demonstrate the principles experimentally in a uniaxial BBO crystal and find excellent agreement between the ex- perimental and theoretical results. The results imply a coupling of the intrinsic and extrinsic optical angular momentum of the resulting fields, which may have importance in studies involving quantum entanglement of the angular momentum basis of light. C 2011 Society of Photo-Optical Instru-

Methods of formation and nonlinear conversion of Bessel optical vortices

Linear and nonlinear processes of generation and transformation of optical vortices in crystals were investigated. New universal methods for production of Bessel light beams with optical vortices of the first, second and higher order by means of uniaxial and biaxial crystals were proposed. Light beams with optical vortices of topological charge +/- 1 and +/- 2 are experimentally obtained using KTP and HIO3 (iodic acid) biaxial crystals. We studied type II second harmonic generation by Bessel beams with optical vortices in nonlinear crystals. Results of investigation of the processes of Bessel light vortex order doubling, transfer of vortex to the second harmonic radiation, and annihilation of optical vortices with the opposite signa are presented.

Generation and propagation of high-order Bessel vortices in linear and non-linear crystals

Linear and nonlinear processes of transferring optical singularities from anisotropic crystals onto the wavefront of Bessel light beams (BLBs) are investigated. The generation of high-order vortices at the propagation of BLBs along the optical axes of crystals was studied. Particularly, a nonlinear frequency doubling of Bessel vortices in the conditions of new type synchronism (full conical phase-matching) is considered. This scheme of three-wave interactions of BLBs based on that the spatial frequency cones of BLBs coincide with phase-matching cones of uniaxial crystals. New type of frequency doubling of Bessel vortices has been experimentally realized in uniaxial crystals.

Methods of formation of gradient light fields

The practical methods of formation of multi-ring and multi- beam gradient light fields are proposed and experimentally realized. These methods are based on the use of crystals, refracting elements with different configurations, and special optical resonators. The obtained gradient light fields have geometrically regular spatial intensity distributions and different types of symmetry. The process of second harmonic generation with gradient light fields was investigated. Gradient light fields and their second harmonic have promising perspectives both for optical information processing and for some technologies, such as cool particles control in nanotechnologies, operations with organic cell and its components, local radiation material processing, and production of some periodic structures.

Methods of formation and conversion of Bessel light beams with wavefront dislocations and applications for optical information processing

New methods for production of pseudo-nondiffracting Bessel light beams with phase singularities of different topological charge have been developed and proved experimentally. It is found out that nonlinear-optical processes of frequency doubling and sum-frequency generation allow to control formation and annihilation of dislocations. The possibility of realization of arithmetic operations using this principle is proved. When Gaussian beam interferes with M-order Bessel beam having M-order dislocation, the dislocation disintegrates on M parallel quasi-nondiffracting beams packed compactly. Rotating of optical beams aggregate on required angle takes place when phase difference between interfering fields is modulated. New principle of optical inter-connections is proposed on this base.

Second harmonic generation by a quadribeam

The scheme for obtaining quadri-beams is studied theoretically and experimentally. In this scheme the quadri- beam is obtained from the plane wave or Gaussian beams using two biprisms. Using optical elements with different number of reflecting planes one can obtain the beams with complex symmetric intensity patterns. The second harmonic generation by quadri-beams is experimentally investigated. The theoretical explanation of the obtained spatial distribution of second harmonic radiation is given.

Simple method of laser beam quality analysis

A method for determining the mode composition a of laser radiation with Bessel mode structure is developed, which includes measurement of intensity distribution and solution of systems of the algebraic equations for amplitudes and phases of partial beams corresponding to different Bessel modes. A method of laser beam quality analysis utilizing a simple optical scheme composed of a telescope, axicon, and microscope is proposed and verified experimentally.

Resonator with Bessel-Gauss modes

We present a new scheme of optical resonator for production of Bessel and Bessel-Gauss beams. This resonator, employing only spherical mirrors and axicons, does not contain any complicated optical elements. Analytical expressions relating parameters of resonator and characteristics of its modes are obtained and analyzed. Diffraction energy losses are calculated with Fox-Li algorithm, and modal discrimination is studied.

Creation and annihilation of wavefront dislocations in the process of frequency doubling of Bessel light beams

We have studied, both theoretically and experimentally, the doubling of topological charge of dislocations of Bessel light beams, transfer of a dislocation to a second harmonic radiation without change of its topological charge, and annihilation of screw dislocations of the opposite sign.

New method of formation of high-order Bessel light beams using biaxial crystals

A new method for obtaining high-order Bessel light beams has been developed and proved theoretically and experimentally. It is based on the phenomenon of transformation of circularly polarized light beam passing through biaxial crystal along its binormal. The method can provide conversion of input Gaussian beam into Bessel beam with an almost 100% efficiency. Besides this method can be used to convert high-intensity laser beams. The light field having the cross distribution in the form of spiral is obtained from the first order Bessel light beams. A possibility of formation of the zeroth and the first order Bessel light beam from Gaussian light beam in biaxial crystal without axicon is investigated theoretically.