KEYWORDS: Particles, Point spread functions, Optical components, Modeling, 3D image processing, Superposition, Image acquisition, Apodization, Signal intensity, Imaging systems
In this paper, a comparative simulation of 3D image formation during phase apodization of an optical system by a zone spiral element and a Laguerre-Gauss (LG) rotating beam generator was is carried out. The formation features of rotating point spread functions (PSF) and their rotation rates were investigated. The obtained results showed that the rotating LG beam has more universal properties in comparison with the beam from the zone spiral element, since the rotation speed can be changed due to the combination of mode indices, while the beam structure is preserved along the whole length. These results can be useful for selecting a 3D imaging method in various applications including optical measurements, coding microscopy.
To analyze the ability of certain beams to maintain information stability under the influence of random fluctuations of the optical medium, numerical calculations based on turbulence simulators such as diffusers, scattering screens and turbulence cells are used. These turbulence simulators can be generated via the Karhunen-Loeve expansion, which is a basis of the eigenfunctions of the correlation operator. In this paper, we consider an analytical calculation of the Karhunen-Loeve functions for a two-dimensional correlation function defined in the form of a Gaussian function, as well as numerical calculation for various four-dimensional correlation functions.
We investigate the generation of closed-packed light rings with a minimum possible diameter using a combination of a light ring distribution generator and a diffractive beam splitter. As a light ring distribution generator, we use the wellknown S-waveplate and generate three different types of ring-shaped laser beams: an azimuthally polarized Gaussian beam, a first-order circularly polarized optical vortex beam, and a first-order linearly polarized optical vortex beam. Our modeling and experimental results show that the azimuthally polarized Gaussian beam is the best solution for splitting in comparison with the other types of beams. These results can be used in applications of high-throughput laser micro- and nanopatterning materials for the fabrication of microlasers by direct laser ablation of a thin film on glass that have great potential in optical communications and sensing applications.
We present a novel type of diffractive optical elements - a nonlinear spiral phase plate whose transmission function is described as exp(iφmn). The light field generated by the element has a spiral-shaped intensity and phase distribution, a non-uniform orbital angular momentum (OAM) distribution and spiral-shaped energy flow. Because of the non-linear azimuthal phase variation, the nonlinear spiral phase plates demonstrate angle-dependent distortion resistance properties. We believe that the proposed nonlinear spiral phase plates will be useful for the realization of OAM-Mode Division Multiplexing in optical communication systems as well as in the area of laser manipulation and laser-matter interaction for fabrication of unique chiral metasurfaces that can be used in optical communication systems too.
Vortex light beams are used to compact data channels because they have orbital angular moments with an infinite number of possible quantum states. This allows the transmission of optical information in a single physical medium by encoding the data by different optical vortices. The aim of the paper is to modeling and analysis the state of orbital angular momentum of laser beams during propagation through free space and parabolic fiber in the presence of random fluctuations of the optical medium. The modeling results for Laguerre-Gauss beams showed that after the beams distortion by random noise, they self-regenerate with further propagation in an undisturbed medium, and it is possible to determine the initial state of the orbital angular momentum of the beam by means of binarization of the field expansion coefficients in angular harmonics.
Vortex laser beams possessing an integer orbital angular momentum are promising for compaction of communication channels in the transmission of information by means of free-space optics. We consider vortex beams representing a superposition of the Laguerre-Gaussian modes with different indices, so they have a fractional orbital angular momentum. Such beams enhance the capabilities and improve the security of information transfer. We consider the propagation of vortex laser beams in a random medium based on the extended Huygens-Fresnel principle. To determine the modal composition of the considered beams under the conditions of random distortions we propose to use multichannel diffractive optical elements (DOE) matched with optical vortices.
We study theoretically the propagation of vortex laser beams in a random medium. The study is based on the extended Huygens-Fresnel principle with the generation of a random field, using the fast Fourier transform. The simulation shows that the stability of vortex beams to fluctuations of an optical medium falls with rising order of optical vortices. A coherence length (radius) of the random medium is of great importance. The coherence radius extension affects adversely the conservation of a beam structure in the random medium. During further free-space propagation, increasing coherence enables to reduce negative effects of fluctuations for beams with high-value topological charges.
The theoretical analysis of optical signal propagation through two-lens imaging system based on double finite Hankel transform of order m was performed. The computation of eigenfunctions of the system considered. This computation gives an opportunity to analyze distortion of the optical signal transmission based on the approximation by functions of this set.
The eigenfunctions of optical operator describing a finite two-lens imaging system are considered accounting for a radial
symmetry. Obtained functions are analogue of the generalized spheroidal functions, which are eigenfunctions of finite
Hankel transform. A peculiarity of the considered calculations of the bounded lens system is in accounting for the
system’s physical characteristics. A possibility of formation of a radially symmetrical optical signal, which transfers
without distortions as a superposition of eigenfunctions matching the parameters of the optical system, is demonstrated.
Gaussian-beam transfers through the imaging systems with circular and with rectangular apertures are compared.
Prolate angular spheroidal functions of zero order and their properties has been considered. The calculation of spheroidal functions has been produced for different parameters. One- and two-dimensional Gaussian beam decomposition into spheroidal functions provided in the paper allowed to evaluate the distortion of the optical signal passing through the lens system. We demonstrate the possibility of the formation of the optical signal transmitted through a lens system without distortion as a superposition of spheroidal functions consistent with the parameters of the optical system.
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