Evolution of the polarization vector in an isotropic multi-mode graded-index optical fiber is investigated theoretically. It is shown that the rotation of the polarization vector increases with increasing axial displacement and the angle of inclination of the incident beam to the waveguide axis according to the quadratic law. The influence of polarization of light beam on its geometrical characteristics at propagation in a two-dimensional isotropic graded-index medium using the methods of coherent states is investigated. In a paraxial approximation taking into account the second order terms in a vector wave equation the expressions for the trajectory and width of linear- and circularly- polarized radiation are obtained. It is shown that the circular polarization leads to the rotation of the propagation plane of the meridional rays and additional rotation of sagittal rays, depending on the axial shift of the incident beam.
The spectrum of modes of cylindrical optical fiber is determined analytically by solving the three-component field Maxwell’s equations using the perturbation analysis. The frequency shift of modes in a graded-index fiber due to nonparaxiality and polarization effects is demonstrated. The degeneracy lifting of modes with distinct orbital angular momentum (OAM) and polarization (spin) but the same total angular momentum due to the spin-orbit (vector) and tensor forces is shown. Generalized Stokes vectors consisting of nine real parameters in terms of irreducible spherical and Cartesian tensor operators are considered to describe the 3D electromagnetic field. Vector and tensor polarization degrees are proposed to characterize the polarized beam.
Theoretical analysis of light diffraction on a periodic structure by using exact analytical solutions of the equations and numerical computer calculations has been conducted. The influence of different apodization functions on diffraction curves of reflection and transmission is studied and their comparative analysis is performed. Complete elimination of oscillating sidelobes and a significant suppression of the “tails” of a diffraction reflection curve are achieved for the specific functions of spatial apodization. The maximum values of the reflectivity of the medium with periodic dielectric permittivity are determined. The effects of light absorption in the crystal and moving gratings on the spectral resolution are evaluated. The Fabry-Perot resonator formed by two spatially-distributed “mirrors” is also studied. A significant increase in spectral resolution of filter due to the spatial variation of the refractive index of the medium is shown. It is shown that the high purity crystals are needed to observe the considered effects. Current technologies allow to obtain the glasses with the absorption coefficient α=10-7 cm-1 at which the spectral resolution Δλ ≈10-2 pm could be reached. This is three orders of magnitude narrower than the resolution of existing acoustooptic AO filters with the same crystal thickness. The considered system (a Fabry-Perot spectral filter combining a Bragg grating mirrors with apodization) can significantly increase the resolution of optical diffraction filters. Complete elimination of sidelobes and a significant suppression of the “tails” of a diffraction reflection curve are demonstrated. These results open perspectives to significantly enhance the resolution of the spectrometers, improve the parameters of mobile devices and communication channels. The results are of practical interest and can be used in the development of new diffraction acousto-optic modulators, AO filters and spectrometers.
The reflection and transmission of TE and TM polarized extremely narrow wave beams which are oblique incident on the dielectric interface are analyzed. Disappearance of the Brewster angle and total internal reflection effects for the strongly focused beams is predicted. The change in beam profile after reflection and transmission for different polarizations, incident beam spots and incidence angles is analyzed. Experiments using NSOM (near-field scanning optical probe) fiber probe with an aperture diameter 50 nm are conducted. It is demonstrated that substantial output light intensity increase occurs at the probe end/glass plate interface.
Different methods for creation of 3D image files, including integral imaging, 2D + z files and 2D images captured at different view angles, are considered. It is found that the disadvantage of the integral imaging method for capturing is the small depth of the 3D image. It is demonstrated that the capturing an object from different angles using a rotating platform and a conventional camera makes it possible to obtain a higher depth. Large 3D images using Full HD multiprojectors and Ultra HD 4K projector are created. 3D displays based on mobile devices are also developed.
Wave-optics and ray-field tracing methods for the simulation of micro-lens arrays (MLAs) taking into account the coherence and polarization effects of light source, randomization of microlens array parameters are implemented. The influence of the parameters of radiation source (wavelength, wavefront curvature, beam radius, coherence radius, etc.) and micro-lens array (periodic or random, aspect ratio, pitch size, refractive index, array surface shape and profile (convex, concave), etc.) on the output parameters (intensity distribution, radiation pattern, optical efficiency) of a diffracted beam is investigated. Numerical simulations of the intensity distributions and spreading angle of a diffracted beam have been carried out. The new ray-field approach based on the coherent states representation is developed for calculation of the optical efficiency of the microlens arrays. Such wave beams can be tracked simply through the arbitrary curved surfaces. User Friendly Interface is developed for introducing initial parameters of light source and MLA array and for graphical and data outputs of simulated results.
Spin-dependent effects on vortex light beams propagating in an inhomogeneous medium are demonstrated by solving the full three-component field Maxwell equations using the perturbation analysis. It is found that the hybrid Laguerre–Gauss modes with polarization-orbital angular momentum (OAM) entanglement are the vector solutions of the Maxwell equations in a graded-index medium. Focusing of linearly and circularly polarized vortex light beams in a cylindrical graded-index fiber is investigated. It is shown that the vortex light beam undergoes an additional transverse force acting differently on circular polarized beams with opposite handedness. The wave shape variation with distance taking into account the spin-orbit and nonparaxial effects is analyzed. Effect of long-term periodical revival of wave packets due to mode interference in a graded-index cylindrical optical fiber is demonstrated.
The possibility of efficiently using metamaterials in acousto-optics has been demonstrated. Diffraction of light in heterogeneous medium with non-uniform spatial distribution of dielectric nanoparticles taking into account absorption of light is investigated. It is shown that by changing the concentration of dielectric nanoparticles in the medium, complete elimination of side oscillations and suppression of the “tails” of the diffraction reflection curve can be achieved. The possibility of controlling the hardware function of acousto-optic devices by changing the material, concentration, size, shape and spatial orientation of the inclusions, as well as the polarization of the incident radiation is shown. It is shown, that extremely large electric field enhancement can be observed in an anisotropic crystal in the presence of spatial apodization of the amplitude or abrupt change in the phase of acoustic wave.
Evanescent and propagating field distributions from a strongly focused wave beam with subwavelength waist wa<< λ as a function of polar angle and distance are investigated. Exact amplitudes and intensities of evanescent Eev and propagating Ep fields, including interference terms, are presented both in near and far field regions. It is shown that the amplitude of Eev decays as exp(-r/wa) in near-field region and evanescent waves do not contribute to the far field in the forward direction as well as in the transverse directions θ = π/2, even though the oscillating evanescent field of the same strength, but opposite in sign to the propagating field, exists in the transverse sheet. A far-field method for characterizing apertures based on the relationship between the relative intensity of propagating modes and a subwavelength aperture diameter is proposed.
Multiview 3D display system consisting of mobile phone screen and optical screen consisting of microlens array film is designed. 3D image files are created and images are demonstrated based on different smartphones with high resolution displays.
Influence of incident light beam coherence on the uniformity in the intensity distribution of diffracted beam by microlens array is investigated. Optical efficiency is calculated for different polarizations. It is shown that the intensity profile and radiation pattern of LED source beam diffracted by periodic micro-lens array are highly uniform and insensitive to the wavelength of incident beam. The spreading angle and output efficiency of the diffracted beam is more sensitive to the aspect ratio of microlens array (MLA). The bigger aspect ratio the higher spreading angle and lower the output efficiency. For a given spreading angle the aspect ratio can be decreased substantially if high-index material is used. Significant influence of wave-front curvature and polarization of incident beam on the reflectance and transmittance is shown.
Multiview 3D display system consisting of four full HD projectors and optical screen consisting of microlens array film is designed. Matlab codes for integration of 2D images captured at different angles into one common 3D file are created and 3D images are demonstrated.
Diffraction of light in heterogeneous medium with non-uniform spatial distribution of dielectric nanoparticles taking into account absorption of light is investigated. Influence of dimensional (geometric) effects of nanoparticles on the reflection and transmission curves is shown. In particular, by changing the concentration of dielectric nanoparticles in the medium, complete elimination of side oscillations and suppression of the "tails" of the diffraction reflection curve is achieved. The possibility of controlling the hardware function of acousto-optic devices by changing the material, concentration, size, shape and spatial orientation of the inclusions, as well as the polarization of the incident radiation is shown.
Splitting of the incident laser beam into multiple beams (spots) is investigated. Evolution of a beam intensity profile with distance is analyzed. It is shown that the angular separation of spots is higher for microlenses with larger number of microlenses per inch or less diameter of the raster. Experimental observations are in good agreement with the calculation results.
In this paper the designs of secondary lenses for LED of reflective and refractive types are proposed for extended sources. The lens surface profile for desired illumination pattern on a screen can be obtained by solving first-order differential equations based on the Snell’s law and the energy conservation. Intensity distributions on a target screen were received by ray tracing using Zemax software. High efficiency ultra-slim lenses with illumination areas exceeding the distance between the LED chip and screen by more than six times are demonstrated for different chip sizes. Aspheric lenticular and two-dimensional microlens arrays are designed using wave-optics and ray-tracing methods. Possibility of development of high resolution and wide viewing angle 3D display based on free-form backlight unit is discussed.
In this paper the multi-view 3D display system which includes the modules of capturing three-dimensional objects, image processing (creation of 3D image files) and display screen for the 3D image displaying based on integral imaging technology is developed. Large display screens using multi-projectors are created. Multi-projector system is used for improving the performance, such as viewing resolution, viewing angle, etc. Preliminary experimental results obtained using Full HD multi-projectors are discussed. 3D display based on mobile devices is also developed. 3D image files are created using 2D + depth files and 2D images captured at different view angles. Images on smartphones Sony 4K (resolution 3840 x 2160) and Samsung and LG (resolution 2560 x 1440) are demonstrated.
In this paper an optical element (image rotating cell) consisting of a single piece isotropic material with three internally reflecting faces for image rotation by the angle 90 degrees is proposed. The principle of operation is based on the geometrical phase effect (Berry phase). It is shown that the rotator made of polymer as well as silica glasses is not affected by the chromatic dispersion in a visible range.
Diffraction of light of a visible spectral range by subwavelength metal gratings is investigated theoretically and experimentally. The diffraction efficiencies of the gratings made of various metals (Ni, Ag, Al, etc.) with different depths of the profile are calculated and measurements are carried out. It is demonstrated that under certain conditions an effect of plasmon resonance occurs, at which a complete absorption of the incident light takes place. It is demonstrated, that the influence of the incident beam width on the diffraction efficiency and the electric field profile of the reflected beam is significant for the incident angles, at which the plasmon resonance occurs. It is shown that the incident beam width must be larger than the propagation distance of the surface plasmon in order to couple energy effectively into the plasmon mode.
The influence of regular longitudinally inhomogeneous sections of the waveguides on the level of modal noise, and its dependence on the degree of both spatial and temporal coherence of the radiation source are investigated using the mode approach. The way to reduce modal noise at the joints of waveguides with matching sections between the waveguides is proposed. It is shown that under the matching condition the complete suppression of modal noise due to the joint is possible. A way to reduce modal noise by using random microlens arrays and holographic diffusers is also proposed.
Propagation of strongly focused light beams in graded-index planar waveguide and cylindrical fiber is investigated using exact analytical solutions of the wave equation. It is shown that high efficiency transfer of a strongly focused subwavelength spot through optical waveguide over large distances takes place with a period of revival (regeneration). Intensity distributions of a focused light beam and focusing efficiency are simulated. Super-oscillatory hot-spots with the sizes which are beyond the conventional Abbe diffraction limit can be observed at large distances from the source. This can provide the possibility to detect optical super-resolution information in the far-field without any evanescent waves. Far-field super-resolution imaging capabilities of a graded-index waveguide are also analyzed. It is shown that the vector-vortex Laguerre-Gauss modes with polarization-orbital angular momentum (OAM) entanglement are the vector solutions of the Maxwell equations in a graded-index cylindrical waveguide. The wave shape variation with distance taking into account the spin-orbit interaction and nonparaxial effects is analyzed. Effect of long-term periodical revival of wave packets due to mode interference in a graded-index cylindrical optical waveguide is also demonstrated.
Glassless multi-view projection display system that combines the modules of capturing three-dimensional objects, image processing (creation of 3D files) and display screen with a holographic diffuser is presented. Optical simulations of lenticular and two-dimensional microlens arrays are performed with the aim to determine optimal lenticular sheets, view angle, view number, depth, etc. Effects of crosstalk and ghost-imaging are studied both numerically and experimentally. Multi-projector system is designed and 3D images on 30-inch screen are demonstrated.
Beam combiners and splitters based on the frustrated total internal reflection, diffraction and refraction effects of light beams are considered. New high efficiency prismatic beam combiner consisting of uniform material is proposed.