The dynamics of the formation and relaxation of microbubbles in a polyacrylamide phantom of tattooed skin under the action of a series of laser pulses with 15-ns duration is studied. It is shown that the growth of microbubbles occurs within a few milliseconds, and their lifetime varies from several seconds to several hours, depending on the water content in the phantom and the fluence (energy density)

A new method is proposed to increase the spectral resolving power of collinear acousto-optical filters by using optical feedback when the light leaving the region of its interaction with a periodic structure formed in the crystal by an acoustic wave returns to the input of the crystal, in which the diffraction process repeats itself many times. The light beam returned to the interaction region changes

The paper describes the design of an optical coherence tomograph adapted for studying the state of the tympanic cavity of the human middle ear. We present the images obtained by the method of optical coherence tomography, which are characteristic of the norm and of the case of pathology – otitis media with effusion.

The possibility of increasing the efficiency of light action during scleral collagen riboflavin/UV photocrosslinking by means of immersion clearing of tissue before UV irradiation is studied. The effectiveness of photo-action is assessed by a decrease in the relative content of the photocrosslinking sensitizer, riboflavin, which is determined from the decay times of tissue fluorescence at different

We report a fast and computationally stable method for computer simulation of optical properties of layered scattering systems containing luminescent layers. The method is based on the solution of one-dimensional scalar radiative transfer equations and makes it possible to calculate spectral and angular characteristics of luminescent radiation emerging from the system under various conditions of luminescence

The results of measuring the derivative of the pulse wave using a laser autodyne based on the Fourier analysis of the lowfrequency spectrum of the interference signal are presented. The features of using the windowed Fourier transform for window types and window widths are discussed. The correlation coefficient between the derivative obtained by direct differentiation of the sphygmographic signal and

Water plays an important role for normal functioning of the skin. The stratum corneum (SC) - the outermost layer of the epidermis - maintains the skin barrier function and regulates the water balance in the organism. Water is non-homogeneously distributed in the SC and its correct determination is important in dermatology and cosmetology. Confocal Raman microspectroscopy (CRM) is the most suitable

A scheme is proposed for measuring electron level populations in a semiconductor quantum dot embedded in a multimode waveguide. The photon transmittance of the waveguide under steady-state pumping is shown to depend on the presence of an electron in the ground state of the quantum dot. The influence of waveguide, quantum dot, and photon source parameters on the electron detection process is examined

The possibility of using bursts of microsecond pulses of an Yb,Er : glass laser (λ = 1.54 μm) for cataract destruction was investigated experimentally in vitro for the first time. The energy in a laser pulse was limited from below by the eye lens destruction threshold and from above by the radiation resistance of the input end face of the radiation-supplying fibre. The energy of a burst consisting

We report a theoretical study of plasmon generation of a giant electromagnetic field in a supernarrow nanoslit formed by a silver cylinder and a flat mirror surface. It is shown that as the silver surfaces approach each other, gap plasmons are excited in the gap between them, which results in a resonant amplification of the field. It is demonstrated for the first time that the electric field amplification

The results of numerical simulation of the near-field distribution inside and in the vicinity of two types of gold nanoparticles (nanospheres and nanorods) intended for producing complexes of gold nanoparticles linked with proteins and exciting photosensitizers in the wavelength range of 532–770 nm are presented. Quantitative estimates of the field localisation (enhancement) are obtained depending

The first issue of the Quantum Electronics journal for 2021 is dedicated to laser biophotonics and features primarily the papers based on invited reports delivered at the International Symposium 'Optics and Biophotonics 2020' (https://sfmconference. org/files/20-sfm-program-5-10-20-total.pdf), which is part of the famous international conference Saratov Fall Meeting (SFM) held annually in Saratov (Russia)

An action of the IR laser pulses with a wavelength of 1.56 μm, moderate intensity, and various durations on a collagen framework structure and sclera tissue permeability is considered. It is shown that the temperature thresholds of collagen denaturation in tissues under the laser irradiation are substantially lower as compared to those under conventional homogeneous heating in a calorimeter oven. A

The efficiency of using silicon nanoparticles, produced by laser ablation of porous silicon in liquids, as agents for hyperthermia of tumours using laser radiation with wavelengths of 633 and 800 nm is evaluated. Using the optical parameters of the nanoparticles suspensions determined earlier by the spectrophotometry measurements, the heating of tumour tissue with embedded nanoparticles is numerically

The results of the operation of a wavefront correction system based on a deformable bimorph mirror of the PEARL subpetawatt laser facility are presented. An improvement in the quality of focusing of laser radiation, which led to an increase in the Strehl ratio from 0.3 to 0.6, is demonstrated. The features of the compensation for phase distortions of the wavefront in the case of a low pulse repetition

A model of coupled modes is proposed, which makes it possible to describe the propagation of a pump wave and a Stokes component in a multimode graded-index fibre. A decrease in the depression in the centre of the profile of the pump wave intensity distribution as a result of the influence of Kerr effects and random linear coupling of modes is demonstrated.

Based on the dispersion relation for a wave localised in a thin film of a nonlinear dielectric, which is located on the surface of a topological insulator, we have derived a system of equations that describes the propagation of a surface wave. It is shown that the longitudinal and transverse tangential components of the electric field vector are related due to the nonlinearity of the film and change

This paper reports results of a study aimed at producing a Raman fibre laser based on a multicore fibre with high-reflectivity fibre Bragg gratings inscribed in its peripheral cores using femtosecond laser pulses. We present spectral and power characteristics of a Raman laser whose output power at a wavelength of 1090 nm is 2.5 W. The laser emission linewidth has been shown to decrease as a result

The feasibility of making a wavelength-selective fibre filter using fibre with absorbing rods in its silica cladding has been demonstrated theoretically for the first time. The technique described in this paper is of great practical interest for designing fibre lasers and amplifiers emitting at wavelengths where lasing is impeded by the presence of more energetically favourable radiative transitions

We consider statistical characteristics of laser interference recorded in the focal region of an IR optoelectronic observation system under field and out-of-field illumination by laser radiation. The applicability of the analytical description of experimental histograms of the laser interference signal distribution at the photodetector array output using the probability density approximations in the

Laser light propagation in a photonic lattice consisting of two parallel waveguide arrays is theoretically studied using the coupled mode method, with the interaction of each waveguide with the nearest neighbours and between the waveguides of the arrays being taken into account. Analytical expressions are obtained that make it possible to accurately predict the presence of localisation of light depending

The effect of 1-s irradiation of an uncooled polycrystalline CVD diamond plate by a focused cw CO 2 laser beam with a power density of 300 – 800 kW cm -2 is investigated. The absorption coefficient of the sample at a power density of 800 kW cm -2 is found to be 0.035 cm -1 larger as compared with that at 300 kW cm -2 , which is related to the temperature dependence of its phonon-induced absorption

The degree of destruction and evaporation of metal films (Au and Ti, thickness ≈50 nm) with a gel layer during laser transfer of small volumes of a gel substrate is estimated depending on the laser fluence value. The dynamics of these processes for dry films and films with a gel layer at fluences close to threshold values is investigated using a probe beam of a He – Ne laser. It is shown that the presence

A method is proposed for the production of two-colour radiation with monochromatic components, the polarisation vectors of which rotate in opposite directions, and the rotation speed is controlled by the sound frequency. The method is based on acoustooptic (AO) interaction upon double passage of two-colour radiation through an AO cell made of a gyrotropic crystal; the method efficiency is demonstrated

Fluorocarbon (C : F) nanofilms up to 60 nm thick are synthesised on a titanium surface. The films are obtained by annealing thin layers of fluorocarbon oil (FO) (with an area of 0.6 cm 2 ) in air with pulsed (80-ns) KrF laser radiation having a fluence of more than 4 J cm -2 . The strength of C : F nanocoatings turns out to be comparable with that of titanium and exceeds several hundred times the corresponding

The output power saturation effect in Yb – Er fibre lasers is experimentally observed. A formula for estimating the saturation power is derived. A method is proposed for measuring the 4 I 11/2 level lifetime or the concentration of Er ions based on the measurements of the saturation power.

A neural network architecture is proposed to determine the number of solitons generated by random processes in optical wavelength-division multiplexed telecommunication systems with QPSK, 16-QAM, 64-QAM, and 1024-QAM modulation. The dependence of the prediction quality of a neural network with a special architecture on the number of soliton modes in the signal and the parameters of this signal is studied

We present an energy scalable configuration for the generation of high-power few-cycle femtosecond IR pulses based on the sequential parametric amplification of chirped radiation pulses at the idler (0.86 μm) and signal (1.39 μm) wavelengths from the multi-terawatt femtosecond laser system made at the Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences (ILP SB RAS). The configuration

We examine multimode diode laser pump depletion in a graded index multimode (MM) fibre Raman laser generating a high-quality Stokes beam. Spatial 'hole burning' in the transmitted pump beam is demonstrated. A balance model is constructed for interaction of the pump and Stokes waves in the MM Raman laser. Analytical formulas are derived and used in calculations demonstrating qualitative agreement with

Semiconductor lasers based on AlGaInAs/InP heterostructures with an ultra-narrow waveguide and an increased electron barrier layer are developed. It is shown that the use of this waveguide in conjunction with profiled doping ensures a balance between internal optical losses and heat resistance. Additional use of strained wide-bandgap layers as blocking barriers limiting electron leakage from the active

A radio-optical synthesiser intended for operation in a radio-frequency master oscillator with an optical He – Ne/CH 4 frequency standard (λ = 3.39 μm) is developed on the basis of a femtosecond erbium-doped fibre laser. The synthesiser generates equidistant harmonics in the frequency range of 1 – 10 GHz with stability determined by the optical frequency standard. A stable supercontinuum spectrum is

We demonstrate a bench-scale prototype of a photoacoustic (PA) methane gas analyser that takes advantage of an optical parametric oscillator (OPO) based on a fan-out MgO : PPLN structure and resonant differential PA detector. The OPO emits in a repetitively pulsed mode (≈1750 Hz) at an idler wavelength of ≈3.3 μm with an average power of ≈40 – 50 mW. Using the prototype laser PA gas analyser, we experimentally

We have experimentally studied the characteristics of a supersonic cw chemical HF laser with a flat nozzle array based on a nozzle – nozzle reagent mixing scheme operating with the use of F 2 – D 2 – He and NF 3 – D 2 – He fuel compositions in an atomic fluorine generator. The active medium flow field pattern, its gasdynamic characteristics, and the laser radiation spectrum are considered. The comparison

We consider the influence of noise parameters of a 3D lidar and external background radiation on the error in estimating the relief signatures of distant objects from 2D field intensity distributions of the reflected radiation. A physical and mathematical model is developed to analyse the effect of noise. The dependence of the error in estimating the relief signatures at various signal-tonoise ratios

We report the results of an experimental study on the focusing of broadband terahertz (THz) radiation using lenses and Fresnel zone plates. The obtained data are compared with the results of numerical simulations. It is shown that the use of lenses for focusing THz radiation can lead to the appearance of a ring structure in the spatial distributions of its intensity. The use of Fresnel zone plates

The decay of the pump-beam spatial structure under conditions of stimulated temperature scattering of a pulsed laser beam in toluene as a result of two-photon absorption of pump radiation and time-dependent interaction of a laser pulse with a medium is considered.

We review the frequency comb generation process, main microresonator parameters such as free spectral range (FSR) and Q-factor, previously used optical frequency comb (OFC) generator parameters and resulting frequency combs, as well as the implementation of OFC for optical data transmission. An optical frequency comb is produced in a setup based on a tapered fibre and a SiO 2 microsphere. The generated

We consider the behaviour of the orbital angular momentum of the light field as a superposition of Hermite–Gaussian beams upon astigmatic mode conversion. An analytical expression is obtained for the orbital angular momentum of such fields. Expressions are found for various linear combinations of Hermite–Gaussian beams. The astigmatic mode conversion of the initial light fields that are equivalent

The temperature conditions for photodynamic therapy of the culture of tumour cells organised in 3D spheroids are studied. The spheroids are placed in the cell culture medium in the well of a special cell culture plate with absorbing walls. A mathematical model is presented that describes the temperature distribution in a well with a cell culture plate heated by optical radiation. It is shown that the

We report on a theoretical model of the effect of coherent population trapping in alkali atoms in an optically thin gas cell with a buffer gas at a nonzero temperature in a pulsed laser field. The shape of the Ramsey resonance is analysed for two different temperature ranges, i. e. for a 'cold' atomic ensemble and for an ensemble of 'hot' atoms in a cell with a buffer gas. The influence of the hyperfine

Sub-Doppler resonances in caesium vapours are studied in a laser field produced by counterpropagating two-frequency light beams with mutually orthogonal linear polarisations. The beams are in resonance with optical transitions in the D 1 line, the frequency difference of the field spectral components being equal to the hyperfine ground-state splitting in the Cs atom (≈9.2 GHz). It has already been

Quantum-cascade room-temperature 4.5 – 4.6 μm lasers with different numbers of quantum cascades are developed and studied. It is shown that losses at the metallised sidewalls of the ridge waveguide considerably increase the threshold current density. It is demonstrated that the current density needed to overcome the internal and outcoupling losses in lasers with 30 quantum cascades is an order of magnitude

Based on the analysis of experimental data on the effect of the pulsed laser pump intensity on the spectral properties and the size of the fluorescent response zone in randomly inhomogeneous fluorescent layers, we found that the amplification of spontaneous and stimulated emission significantly affects the statistical properties of the propagation lengths of the fluorescent field partial components

A triple laser–thyristor, i. e., a semiconductor laser with three emitting sections monolithically integrated with an electronic switch (thyristor) is experimentally studied. For comparison, the output characteristics of single and double laser–thyristors are presented. It is shown that the functional integration of a laser with a thyristor in one heterostructure allows the laser to efficiently operate

A theoretical formula is derived that makes it possible to establish a relationship between the speed and sensitivity of bolometers with geometric and thermophysical parameters of the receiving element and substrate. The result is confirmed by a preliminary (evaluation) experiment. The proposed thermal detectors can record and measure the radiation power of lasers and generators of the submillimetre

The luminescence of Xe 2 Cl* excimer upon optical excitation of high-pressure Cl 2 – Xe mixtures by XeCl laser pulses (λ = 308 nm) with different energies is investigated. It is shown that small-signal gain of the Xe 2 Cl amplifier may reach ≈1.3 × 10 -1 cm -1 in a mixture of Cl 2 and Xe with partial pressures of 4 Torr and 9 atm, respectively, and an excitation fluence of 10 26 photons cm -2 s -1

We have revealed a strong (by a factor of 2 to 5) mutual increase in the yield of IR molecular dissociation (by the example of CF 2 HCl and CF 3 Br) and a significant (by a factor of 1.5 to 3) lowering of dissociation thresholds in the nonequilibrium thermodynamic conditions of compression shock in the irradiation of the molecules by resonance IR laser radiation in the bimolecular mixture in comparison

We propose using wavelength-modulation laser absorption spectroscopy in combination with quadrature detection of scattered light for remote industrial pollution monitoring in the atmosphere with a compact lidar-based gas sensor, which can be mounted on board an unmanned aerial vehicle. The instrument can be used for detecting leaks in product pipe lines; monitoring toxic gases near landfill sites,

The specific features of efficient matching of acoustooptic devices with single-mode fibres for the cases of isotropic and anisotropic diffraction are considered. The acousto-optic interaction geometry, optimal for modulating an arbitrarily polarised light beam with a possibility of tuning its frequency shift in the range up to ≈10 MHz, is chosen. Acousto-optic modulators/frequency shifters based on

A family of aperiodic Mo/Be multilayer mirrors was designed for maximum uniform reflectivity in the ranges 111–138, 111–150, 111–200 and 111–222 Å at normal radiation incidence. The simulations took into account the existence of Mo-on-Be and Be-on-Mo transition layers. It was shown that the reflectivity may be as high as 10% in an octave wavelength range of 111–222 Å. We demonstrate the operation of

A method for realising a universal system of quantum gates based on asynchronous excitations of two-level atoms in optical cavities is proposed. The entangling operator of the CSign type is implemented without beam splitters, approximately, using the incommensurability of the Rabi oscillation periods in a cavity with single and double excitations.

Numerical simulations were used to investigate the electron bunching induced by a laser pulse in its penetration into a plasma that has a nonuniform density profile at the vacuum – plasma boundary, which reaches a plateau. A mechanism was found to exist for this plasma which fosters a denser electron grouping in the generated bunch in comparison with the plasma with a sharp boundary. This mechanism

Interference of wave trains separated out in an inhomogeneous emission spectrum of a superluminescent erbium-doped fibre source has been studied by scanning the wavelength of a spectrum analyser. The results demonstrate that, as the spectral resolution of the spectrum analyser decreases to a level corresponding to a sharp drop in interference fringe visibility relative to its original level, near 100%

The effect of defocusing due to the finite thickness of the crystal, in which parametric scattering occurs, on the spatial resolution of ghost images is considered. The necessary relationships are presented, and methods of levelling this distorting factor and improving the quality of ghost images are proposed.

We report a study of the process of nonlinear Thomson scattering (NTS) of a tightly focused relativistically intense laser pulse by an ensemble of electrons simulating the result of ionisation of an ultrathin nanofoil. The description of all six components of a laser pulse is based on the Stratton – Chu integrals describing radiation focused by an off-axis parabolic mirror into a spot down to the diffraction

It is shown that the use of a toothed nozzle array in the active medium generator (AMG) of continuous-wave chemical lasers (CWCLs) allows more efficient mixing of reagents to be achieved in the laser chamber than in an AMG with a slit nozzle array. The results of calculations of parameters of the active medium of a DF CWCL operating in the gain regime for the AMG with traditional and promising nozzle

Different modifications of acousto-optic modulators (AOMs) based on KG(WO 4 ) 2 (KGW) and KY(WO 4 ) 2 (KYW) crystals, designed for Q switching of high-power pulsed lasers, is developed and investigated. It is shown that AOMs based on these crystals are universal, can be combined with different lasers in the wavelength range of 1–3 mm, and have a high radiation resistance in the absence of antireflection

The peculiarities of Ramsey resonance and its sensitivity to the light shift from an optically dense medium of cold atoms are investigated. Different composite pulse protocols for clock spectroscopy, including hyper-Ramsey, modified and generalised hyper-Ramsey schemes, are compared. Error signals change significantly due to the processes of absorption and dispersion in the atomic medium. The dependence

A brief review is presented of investigations performed in 2002–2020 on ultraviolet inactivation of bacteria, vital cells, and viruses by using excilamps. The excilamp models that have been developed at the Institute of High-Current Electronics, SB RAS are briefly described. Scientific data acquired by now show that excilamps on KrCl *, KrBr*, and XeBr* molecules are an alternative to low-pressure

We have prepared aluminophosphate glass samples differing in bismuth oxide content and demonstrating broadband near-IR photoluminescence. Analysis of their photoluminescence spectra leads us to conclude that they contain two main types of emission centres, one of which seems to be a bismuth monocation and the other is a cluster ion. In addition to these luminescence centres, the aluminophosphate glasses