Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Mode discrimination of unstable resonators with spatial filters and by phase modification.

Abstract: The effects of an intracavity spatial filter in a half-symmetric unstable bare cavity resonator have been studied using iterative propagation techniques to obtain pure l-mode resonator solutions. The results indicate that the mode-loss difference is highest when the spatial-filter radius is at the first or third dark ring of the Airy pattern at the spatial filter. Furthermore, the results are not directly dependent on the resonator-equivalent Fresnel number. Also presented are results indicating that aspherizing the feedback mirror can be done in such a way as to increase mode discrimination.

An SVD Approach for Estimating the Dimension of Phaseless Data on Multiple Arcs in Fresnel Zone

Abstract: In this article, we tackle the question of evaluating the dimension of the data space in the phase retrieval problem. With the aim to achieve this task, we first exploit the lifting technique to recast the quadratic model as a linear one. After that, we evaluate analytically the singular values of the lifting operator, and we quantify the dimension of the data space by counting the number of “significant” singular values. In the last part of the article, we show some numerical results in order to corroborate our analytical prediction on the singular values’ behavior of the lifting operator and on the dimension of the data space. The analysis is performed for a 2D scalar geometry consisting of an electric current strip whose square magnitude of the radiated field is observed on multiple arcs of circumference in Fresnel zone.

Mirrors with point-spread functions that exhibit wavelet-related characteristics.

Abstract: Mirrors with amplitude point-spread functions that exhibit wavelet-related characteristics are profiled by the method of stationary points and the method of Fresnel zones. The unknown optical path function ϕ(r) of the diffraction integral is reconstructed from its stationary points, which are identified from locations where the pupil function of the optical system is an extremum. The ϕ(r) that describes the paths taken by the light from the point source to the observation plane via the reflecting surface is used as a constraint in the procedure. In particular, circular distributions of the Mexican-hat wavelet and the Fourier transform of the Haar wavelet are considered for the point-spread functions.

Elliptical Bessel-like diffraction pattern produced by circular apertures with different radius

Abstract: We present the results of the amplitude diffraction pattern produced by two circular apertures. It was found that on the Fraunhofer plane there are is a diffraction pattern with an elliptical geometry with a Bessel-like spatial distribution modulated by Young fringes. The model was experimentally confirmed using circular apertures illuminated with a Helium-Neon laser and propagating to either the divergent Fresnel zone and the Fraunhofer plane using an achromatic cemented doublet as transforming lens.