Subject of study. A holographic system with a tunable convergence angle of two interfering light beams, based on a beam-splitting cube and intended for writing diffraction gratings, is investigated analytically. The initial light beam is introduced into the cube using a movable mirror, which performs both linear and angular displacements, because of which the convergence angle is tuned. A lever mechanism leaning on an inclined guide is used for the movable mirror's combined movement. Aim of study. The primary aim is to find a matching technique for the displacements of the movable mirror that ensures the resulting interference grating created in the plane of complete mutual overlap of converging beams remains immobile when the convergence angle is adjusted. Method. The path of light beams in the system was analyzed within the framework of geometric optics. Main results. It was found that the contact profile of the guide must be curvilinear to fix the spatial position of the interference grating. The precise functional relationship describing the envelope of this profile is derived, and the tuning characteristics are calcu-lated based on the relative position of the photosensitive sample with respect to the beam-splitting cube. Practical significance. The design of this holographic system presents the advantage of using light beams of various diameters without requiring system corrections.(c) 2023 Optica Publishing Group

Two-beam interferometer with fixed mirrors and fixed recording media, analytical analysis of optical scheme and design of the construction are presented. Tuning of the spatial frequency of the interference pattern on the media is carried out by rotation simulation mechanism. A working sample device of interferometer based on a beam-splitting cube 20 mm in size and implementing the investigated concept has been created. In the device, a half of convergence angle of interfering beams with a diameter of 5 mm is tunable in the range from 11 to 19, its value is setting using a degree scale with a resolution of 0.1. The deviation of actual value of the angle through the scale reading is experimentally obtained in the device. It was found that the absolute error does not exceed 1%. Developed interferometer may be useful an instance in holographic (including liquid) materials studies, devel-opment a new design of static Fourier spectrometers and making the interference based lithography process.

A photosensitive charge transfer complex (CTC) is formed between the components of the photopolymer material: the tetra-acrylate monomer synthesized from dihydroxydiphenyl sulfide (TADDS) and a photoinitiator, a cationic sulfonium salt synthesized from diethylthioxanthen-9-one (SSDETX). It allows one to perform laser recording of the microstructures in the hybrid photopolymer material using absorption of CTC at lambda=473 nm. The 1 : 1 molecular composition of CTC was confirmed by applying the Job's method of continuous variation to determine the stoichiometry. The association constant (K-AS(278 degrees K)=17 L mol(-1)) was calculated using the modified Benesi-Hildebrand equation. The thermodynamic parameters, such as enthalpy (Delta H=-15.63 kJ mol), entropy (Delta S degrees=-32.6 J mol(-1) K-1), and the Gibbs free energy (Delta G=-6.63 kJ mol(-1)) were calculated using the Van't Hoff equation. These results indicate that CTC formation is an exothermic reaction. The experimental findings were supplemented by density functional theory (DFT) study of CTCs at the UB3LYP/6-311G level as implemented in the Gaussian 09 software package. Charge transfer excitations were simulated by means of the time-dependent density functional theory (TDDFT) approach. The DFT-calculated spectra agree with the experimental data of spectral and photochemical properties of the [SSDETX-TADDS] CTC.

ПЕРЕСТРАИВАЕМЫЙ ДВУХЛУЧЕВОЙ ИНТЕРФЕРОМЕТР НА ОСНОВЕ КВАРЦЕВОГО СВЕТОДЕЛИТЕЛЬНОГО БЛОКА, ОСНАЩЕННЫЙ НЕПОДВИЖНЫМ ФОТОПРИЕМНИКОМАналитически исследован двухлучевой интерферометр на основе симметричного светоделительного блока из кварцевого стекла с неподвижными зеркалами, оснащенный неподвижным фотоприемником.В интерферометре возможна широкополосная перестройка пространственной частоты записываемой интерференционной картины.Ее положение стабильно в процессе перестройки благодаря взаимному согласованию линейного и углового перемещений исходного светового пучка

Двухлучевые интерферометры с возможностью варьирования периода записываемых дифракционных решеток широко востребованы в различных областях голографии и фотоники, например, для исследования свойств фотополимерных материалов и записываемых в них голограмм [1], для записи в оптических волокнах массивов распределенных брэгговских решеток (ВБР) в качестве датчиков физического состояния волокна [2] и для других применений.В [3] описан интерферометр на основе светоделительного кубика (СДК) с двумя зеркалами и фотоприемником (ФП), неподвижными относительно СДК, в котором стабилизация положения интерференционной картины (ИК) при варьировании угла схождения парциальных световых пучков (ПП) обеспечивается взаимно согласованными линейным и угловым перемещениями подвижного зеркала (ПЗ), направляющего световой пучок в СДК.Такие интерферометры удается объединять в системы для записи двумерных решеток с независимой установкой периода в каждом измерении [4].Однако для записи протяжённых ВРБ (10-15 мм) более подходящим представляется интерферометр на основе светоделительного блока (СДБ) [5], поскольку в нем длина хода световых пучков в материале СДБ более чем в 3 раза короче по сравнению с СДК соответствующих габаритов.Целью данного доклада является анализ перестройки периода в интерферометре на основе СДБ из кварцевого стекла при стабилизации положения ИК, обеспечиваемой согласованием линейного и углового перемещений ИП на входе в СДБ посредством механизма имитации вращения [3].На рис. 1 представлена оптическая схема исследованного интерферометра, ход световых пучков отображается их осями.Интерферометр, включающий в себя СДБ 1 и два зеркала 3.1 и 3.2, оптически связан с ФП 4, который удален от торца C 2 C 3 на расстояние L ph .СДБ представляет собой две плотно состыкованные рабочими поверхностями идентичные пластины из кварцевого стекла длиной M и толщиной A  0,15M с делительным зеркалом (ДЗ) 2 между ними.Зеркала установлены симметрично к плоскости ДЗ на расстоянии H друг от друга под углом  (на рис. 1  > 0).Исходный световой пучок (ИП) 7 диаметром D направляется на входную поверхность C 1 C 2 на расстоянии Q от края C 1 под углом падения  посредством ПЗ 5 и Рис. 1. Оптическая схема интерферометра

Within the framework of geometric optics, this study analyzes the rotational tuning of the period of an interference pattern formed by converging light beams on a photodetector that is fixed relative to a mirrorless two-beam interferometer based on a beam-splitting cube. Equations are derived, whose solutions are the dependences of the tuning range on the base position of the initial light beam on the input surface of the cube and on the diameter of this beam. These dependences are obtained for several refractive indices of the cube material, and the significance of this parameter for the characteristics of the interferometer under study is shown.

A tunable (in terms of the angle of convergence of intersecting light beams) two-beam interferometer with fixed mirrors and a fixed photosensitive element is considered. The photosensitive element is based on a symmetric beam-splitter unit where tuning of the interference pattern period is ensured by only one type of motion: interferometer rotation with respect to the motionless source of the collimated light beam. It is demonstrated that the period can be controlled in this way for convergence angles from 30 to 180° for beams with diameters of 10% or more of the beam-splitter unit length. In this region, the greatest width of the range of convergence angle tuning can exceed 40°, and the admissible beam diameter approaches 40% of the beam-splitter unit length. Comparisons with a similar interferometer based on a beam-splitter cube are performed, and possible areas of application of the considered interferometer are determined.

Results of calculations of the limiting characteristics of a rotationally tunable two-beam interferometer on the basis of a beam-splitter cube with fixed mirrors and a fixed photosensitive element are presented. The convergence angle is changed solely by rotating the beam source with respect to the interferometer. It is shown that the convergence angle can be varied in the interval from 46 to 166° with sufficiently wide light beams.

This paper presents a holographic interferometer configuration with inclined fixed mirrors based on a beam-splitting unit in which the convergence angle of the partial beams is tuned only by rotating the interferometer relative to the radiation source. The continuous range of tuning is close to the maximum possible (0–180°). The path lengths of the interfering beams are automatically aligned due to the mirror symmetry of the system. The position of the axis of rotation providing minimal aperture limitations in almost the entire range of tuning is determined. A comparison is made with an alternative configuration based on a beam-splitter cube.

Results of analysis of a very simple, compact interferometer for recording holographic diffraction gratings, which allows continuous tuning of the angle between the interfering beams from 0° to 80°, are presented. The device consists of a single optical element, a beamsplitter cube. The lengths of arms in such an interferometer are automatically equal, and tuning is accomplished by changing the angle of incidence of the beam on the input face. Formulas for calculating the principal characteristics of the device are derived. It is shown that using a cube material with a higher index of refraction allows increasing the beam diameter and broadening the tuning range. Recommendations on the device design are provided.

The generation in a laser with an active element made of a neodymium-doped potassium — gadolinium tungstate crystal Nd3+:KGW in the form of a parallelepiped with a coaxial hole for a pump flashlamp is studied. The effect of anisotropy of spectral and laser properties of a Nd3+:KGW laser and of the thermal inhomogeneity of the distribution of laser emission on the output mirror is experimentally demonstrated under conditions when the pump radiation virtually does not return to the medium (the unlimited aperture model).

A strong (by a factor of almost 100) narrowing of the spectrum was observed in quasi-stady operation of a solid-state laser with neodymium-doped potassium gadolinium tungstate when the cavity contained a negative feedback loop and a slow-response saturable absorber, The role of a nonlinear narrow-band selector, which reduced the width of the spectrum, was played by a periodic saturated-absorption grating formed by a standing intracavity laser radiation wave in a lithium fluoride crystal containing F-2(-) colour centres and used as a saturable absorber.

Trains of stable reproducible picosecond light pulses were obtained with a laser on the neodymium ions activated potassium-gadolinium tungstate single crystal, using stationary passive mode-locking technique. A single cavity-dumped pulse of not more than 5 psec duration was amplified up to approximately 10 mJ under repetition rate about 1 Hz in a wide- aperture active element made of the same material.