In this work, using the finite differences time domain (FDTD) method, we calculated the diffraction of a polarized Gaussian laser beam both on a set of elliptical and circular dielectric plates rotated relative to each other which can be considered as a twisted waveguide. The possibility of forming beams resembling a helical photonic jet and light traps is shown.
It is proposed to use an iterative algorithm based on a ring spectrum and a lens to calculate a diffraction-free beam with a given transverse intensity distribution. In this work, we calculated and studied diffractive optical elements (DOEs) that form some primitive non-diffraction distributions (for example, a square and a triangle, as well as more complex grayscale distributions). It is shown that the iterative algorithm is stagnating, i.e. the number of iterations is directly related to the root mean square error. The mean square deviation of the formed transverse intensity distribution from the given primitive does not exceed 0.006 for a triangle primitive, 0.015 for a square primitive, and 0.07 for a high-contrast halftone image.
It is known that the astigmatic transformation is used to analyze the topological charge of a vortex beam. In this paper, to implement astigmatic transformations of vortex beams, a multichannel filter is used, which is matched to various aberrations described by Zernike polynomials. Such a filter allows several wave aberrations of various types and levels to be introduced into the analyzed vortex beam at once in order to implement various aberrational transformations, including astigmatism. In this case, a set of aberration-transformed distributions of the analyzed vortex beam is formed in the focal plane in different diffraction orders, which facilitates the determination of the vortex topological charge.
Recently, data mining and neural networks are increasingly used for wavefront recognition from interferograms. In this case, there is considerable freedom in choosing the structure of the reference beam. In this work, a comparative study of the effectiveness of using neural networks for solving the problem of recognizing wavefront aberrations based on linear (flat reference beam) and conical (conical reference wavefront) interferograms is carried out. The effectiveness of recognition of types and levels of aberrations by conical interferograms based on the use of neural networks is shown: the average absolute error is reduced by 3 times, compared with linear interferograms. This effect is related to the rotational invariance of the introduced aberrations.
This article explores the possibility of improving the detection of spatial anisotropy and visualization of weak wave aberrations when the lens is supplemented with a diffractive axicon. Fresnel transforms are used to simulate the formation of intensity distributions at different distances from the input plane. The results of numerical simulation of diffraction by a composite element (lens and axicon) under illumination by an aberrated wavefront are presented. A significant increase in the efficiency of visualization of weak wave aberrations is shown when using the proposed method based on the deviation of the intensity pattern for an aberrated and ideal wavefront.
In this paper, we investigate a wavefront sensor based on the optical expansion of the analyzed field in the basis of Zernike functions using a multichannel diffractive optical element. Correlation peaks at the centers of diffraction orders correspond to the detection of specific aberrations in the analyzed field, and the peak intensity corresponds to the magnitude of the aberration. The analysis of the threshold sensitivity of the considered wavefront aberration sensor is carried out. In a number of numerical experiments, the threshold value of the sensitivity of the sensor under consideration was obtained. It turned out that when analyzing wavefront aberrations, spurious aberrations can be detected when the wavefront deviation exceeds a certain threshold value, and this value varies for each type of aberration.
We investigate the diffraction of a polarized light by nonlinear spiral phase plate (NSPP) in the near zone, taking into account the three-dimensional structure of the optical element. The simulation of the NSPP diffraction is based on the finite difference time domain (FDTD) method. The results of numerical simulation of the NSPP diffraction for both homogeneous (linear and circular) and inhomogeneous (radial and azimuthal) polarized light are presented.
In this paper, we study the possibility of forming beams with a scalable wavefront. To multiply the wavefront with a scale factor, it is proposed to use a combination of the wavefront distribution generator and a diffractive grating with binarization operation. It is shown numerically and experimentally using spatial light modulator that such beams as the Zernike basis functions and Airy beams are suitable for testing optical systems.
A new approach is proposed to implement phase contrast Zernike filter with dynamic transparent for phase objects visualization. We investigated the effect of the radius size of the filter at the low and high phase distribution of objects in the input plane to the spatial intensity distribution. A significant increase in contrast is shown when using the proposed dynamic filter. The experimental results of the dynamic phase-contrast filter Zernike are consistent with the numerical simulation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.