Search

This paper investigated the diffraction of a Gaussian laser beam on a binary mask and a refractive axicon. The principles of the formation of a zero-order Bessel beam with sharp drops of the axial field intensity edges were discussed. A laser optical system based on an axicon for the formation of a Bessel beam with quasi-uniform distribution of axial field intensity was proposed. In the laser optical system, the influence of the axicon apex did not affect the output beam. The results of theoretical and experimental studies are presented. It is expected that the research results will have practical application in optical tweezers, imaging systems, as well as laser technologies using high-power radiation.

Optical variosystems that form the required diameter of the Gaussian beam waist and perform its smooth longitudinal movement with a constant diameter for laser technologies, processing materials, moving microobjects, etc., are considered. A combined method based on a movable tunable-focus lens for changing the optical characteristics of laser variosystems is proposed. The features and fundamental differences between the laws of transformation of Gaussian beams by optical systems of different structures for the dimensional synthesis of laser variosystems are discussed. Based on these laws and the theory of laser optics, a method for the dimensional synthesis of one- and two-component laser variosystems is developed, an algorithm for their automated synthesis, and an example of calculation are given.

Optical tweezers use a special class of light beams – the so-called Bessel beams. The field amplitude of these beams is described by the Bessel function of the first kind of a zero order. The traditional method of forming zero-order Bessel beams involves the use of a classical optical element – a conical axicon lens. We designed and assembled an experimental test bench to study the parameters of the Bessel beam formed by the axicon. In the course of experimental studies, it was confirmed that Bessel beam is a diffraction-free beam. In addition, an influence of a divergence of the Gaussian beam at the axicon input on the parameters of the Bessel beam was investigated. The transformation of such a beam by an optical system was considered. It is shown that when the Bessel beam is transformed by an optical system, the principle of similarity of optical fields in the optical conjugate planes is fulfilled. The results of modeling the formation of the Bessel beam by the axicon obtained in this work are consistent with the experimental studies.

On the basis of the scalar diffraction theory, the problem of calculating the characteristics of a laser beam in linear cavities of arbitrary configuration, taking into account the aberrations of the mirrors, is solved. The configurations of cavities in which the aberrations of the mirror surfaces have a significant influence on the characteristics of the formed laser radiation are determined.

This paper presents a modeling approach of a laser varifocal system for longitudinal Gaussian beam waist shifting. The developed approach is based on laser optics theory, which is considered to be classical optics generalized for coherent radiation. A basic optical system, consisting of two components, was developed using this theory. Components have fixed focal lengths and specific movements. An automated modeling algorithm was proposed, and an example was provided in text. Various systems shown in this paper form a Gaussian beam with required waist parameters and provide its longitudinal shifts, which exceed the length of the near-zone of a focused Gaussian beam. Such systems can be used in laser technologies, including micro- and nano-sized objects manipulation.

When designing high-quality optical systems, it is necessary to calculate the real field distribution of the output beam. In this work, the solution of this problem by the method of the scalar theory of diffraction is considered. For calculate the diffraction integral and visualize the results, the software package Mathematica (Wolfram Mathematica) is used. Aberration analysis of laser optical systems and simulation in the program Mathematica of the output field distribution showed a significant distortion of the field distribution and deviation of the spatial beam parameters from the ideal one, described by analytic expressions.

A practical method is proposed and developed for calculating characteristics of the laser beam formed by stable and unstable cavities of an arbitrary configuration.

New experimental and theoretical results for the material parameter reconstruction using terahertz (THz) pulsed spectroscopy (TPS) are presented. The material parameter reconstruction algorithm was realized and experimentally implemented to study the test sample. In order to both verify the algorithm and to estimate the reconstruction accuracy, test sample material parameters obtained with the TPS were compared with the results of the same sample studying by the use of the backward-wave oscillator (BWO) spectroscopy. Thus, high reconstruction accuracy was demonstrated for the spectral range, corresponding to the BWO sensitivity and located between 0.2 and 1.2 THz. The numerical simulations were applied for determining the material parameter reconstruction stability in the presence of white Gaussian noise in TPS waveforms as well as fluctuations in the femtosecond (FS) optical pulse duration. We report a strong dependence of the inverse problem solution stability on these factors. We found that the instabi...

This paper presents a technique of aberrational synthesis of laser optical systems with small wave aberrations for maintaining similarity of the fields when multimode laser beams are being transformed. The minimization of the wave aberrations of laser optical systems is based on the detected connection of its design parameters with the expansion coefficients of the wave aberration. Examples are given of the automatic synthesis of laser optical systems to illustrate the effectiveness and high response rate of the proposed algorithm.