Preface

General Information This volume of the Journal is devoted to the IX International Symposium and Young Scientists School “Modern Problems of Laser Physics” (MPLP-2021)1 that was held in Novosibirsk, Russia, 22-28 August 2021. The MPLP symposium has a long history starting from 1995 and gathers scientists from many courtiers who carrying out their researches in the forefront of laser physics, quantum metrology and high-resolution spectroscopy, physics of ultracold atoms, molecules and ions, atom optics, ultrafast phenomena and attoscience, quantum optics and information, nonlinear optics and applications of laser radiation from THz to UV radiation ranges in medicine, geophysics, chemistry and microbiology. This year the sessions devoted to advances in laboratory space plasma physics with lasers was also included in the list of topics of MPLP symposium. The Scientific Program of MPLP-2021 includes invited and oral talks selected from contributed papers, as well as several Poster Sessions. A Scientific School for Young Scientists was also take place during the Symposium. Following the tradition of MPLP Symposia, the scientific program comprises single sessions of invited and oral presentations for each topic, running sequentially. This year online access to MPLP was provided for participants who can’t attend the symposium in-person and many of the invited talks were done online. List of Organizers, Committees, Chairman of the Symposium, Invited and Oral Speakers, School for Young Scientists and Results are available in this pdf.

Laser Transverse Modes with Ray-Wave Duality: A Review

We present a systematic overview on laser transverse modes with ray-wave duality. We start from the spectrum of eigenfrequencies in ideal spherical cavities to display the critical role of degeneracy for unifying the Hermite–Gaussian eigenmodes and planar geometric modes. We subsequently review the wave representation for the elliptical modes that generally carry the orbital angular momentum. Next, we manifest the fine structures of eigenfrequencies in a spherical cavity with astigmatism to derive the wave-packet representation for Lissajous geometric modes. Finally, the damping effect on the formation of transverse modes is generally reviewed. The present overview is believed to provide important insights into the ray-wave correspondence in mesoscopic optics and laser physics.

МЕТОД КЛАСИФІКАЦІЇ ЗАДАЧ ОПТИКИ ТА ЛАЗЕРНОЇ ФІЗИКИ

In recent decades, due to the use of computer technology, the results of research in a particular area of science and technique are accumulated very quickly. In the process of creating a database of optical images and knowledge base is appeared the task of classification method absence. Without such a method the creating the structure of data warehouse is difficult to solve. The classification of the tasks and the obtained results requires considerable attention in order to ensure their rapid and accurate search and further use. Classification is one of the most important tasks of large database analysis used in Data Mining. Assessment of classification accuracy can be performed using cross-checking or a test set. The proposed method is suitable for use when the accuracy of the test set classification meets the established requirements. In the field of optics and laser physics dealt with the problem, which usually is grouped by the next attributes: the initial field pattern, the type of the optical system, the characteristics of the obtained spatial distribution of light as the number of maxima, minima, zeros of intensity and other significant objects. The question of classification of the tasks themselves was considered in the paper for the first time. The method of classification of problems in optics and laser physics is developed. It is applied to the problems of diffraction, interference and observation of microobjects. The classification is carried out with the help of mathematical methods, a formal description of the objects and the decision trees method. The 5 classes was chosen: "meaning the task", "solution method", "appointment", "complexity", "way of expression." The attributes of the problem classification are "visual-optical", "optical", "computational", "experimental", "qualitative", "fundamental", "applied", "simple", "complex", "textual", "numerical", "graphical". The scheme of problems in optics and laser physics classification is shown. Decision-making to determine the attributes of the problem is carried out using the decision trees method. Application of the results in search engines of big databases and pattern recognition problems is discussed.

Minimal Universal Model for Chaos in Laser with Feedback

We revisit the model of the laser with feedback and the minimal nonlinearity leading to chaos. Although the model has its origin in laser physics, with peculiarities related to the [Formula: see text] laser, it belongs to the class of the three-dimensional paradigmatic nonlinear oscillator models giving chaos. The proposed model contains three key nonlinearities, two of which are of the type [Formula: see text], where [Formula: see text] and [Formula: see text] are the fast and slow variables. The third one is of the type [Formula: see text], where [Formula: see text] is an intermediate feedback variable. We analytically demonstrate that it is essential for producing chaos via local or global homoclinic bifurcations. Its electronic implementation in the range of kilo Hertz region confirms its potential in describing phenomena evolving on different time scales.