Periodic modulation of intracavity losses is shown theoretically to result in a change in the shape of the alternating frequency dithering created in a Zeeman ring laser when a magnetic field is applied to the active medium. A mechanism is proposed of a vibrational zero shift in a Zeeman laser gyroscope due to modulation of intracavity losses during vibration of the resonator mirrors.

We report the results of a study of a multimode semiconductor laser gyroscope (MSLG) with a long fibre-optic ring cavity (RC) and alternating frequency dithering formed by a lithium niobate phase modulator, and discuss the factors that determine the device operation. The fundamental limitations in MSLG operation are phase fluctuations and the multimode nature of radiation. Phase fluctuations caused

The possibility of implementing logical operations with images using the accumulated echo hologram in the presence of external spatially inhomogeneous electric fields is considered. It is shown that the photon echo locking effect makes it possible to control the execution of logical operations (from the union of sets to the symmetric difference and their superposition), as well to control their form

The deposition of silver on the surfaces of micro- and nanoparticles of zirconium, molybdenum, and their oxides, obtained by laser ablation of pure metals in aqueous solutions of silver nitrate, is investigated experimentally. Different irradiation regimes and reagent concentrations are approved. The experimental results indicate a possibility of continuous or partial coating (decorating) with silver

The effect of the size of the rods at the structured silicon target surface on the parameters of the plasma produced when the target is exposed to a high-contrast femtosecond laser pulse with an intensity of 2 1018 W cm-2 is investigated. It is shown that irradiation of a target with subwavelength rods (≈100 nm in diameter) provides a significant (up to 250 keV) increase in the temperature of hot plasma

We propose a model of a bipolarised Nd : YAG laser with partially polarised pump radiation, providing competitive amplification of polarisation modes. A new type of instability is predicted, similar to the one that was first observed in [1]. The possibility of experimental verification of predictions is discussed.

We examine the effect of the pump-induced loss in the gain medium of a Rhodamine 6G laser on the spectral dependence of the laser efficiency under microsecond coherent pumping. It is shown theoretically and experimentally that the pump-induced loss is mainly due to nonlinear refraction and thermo-optic inhomogeneities of the gain medium, which produce a negative thermal lens, whose defocusing effect

The influence of saturable absorber parameters on the operation regimes of a dumbbell-shaped thulium fibre laser is studied. As saturable absorbers, polymer films with nanotubes characterised by different transmission coefficients in the saturated and unsaturated states are used. The operation of lasers with absorbers of different configurations used to obtain stable Q-switching and mode-locking regimes

We present the derivation of simple analytical expressions for calculating the widths of Rydberg states with small orbital angular momenta in Zn+, Cd+, Hg+ ions of group IIb of the periodic system of elements induced by blackbody radiation (BBR) at ambient temperatures from 100 to 3000 K. The probabilities of radiative transitions from excited nS, nP, nD and nF states to all dipole-accessible states

An elementary algorithm of quantum phase estimation based on the modified Kitaev algorithm is implemented on two qubits of an IBM quantum processor. This algorithm includes adiabatic preparation of the initial state, controlled phase shift with allowance for the results of previous measurements of qubit states, and single measurement of the qubit quantum state in order to obtain each significant bit

We analyse stationary current of the bosonic particles in a flux rhombic lattice connecting two particle reservoirs. For vanishing interparticle interactions the current is shown to monotonically decrease as the flux is increased and become strictly zero for the Peierls phase equal to π. Nonzero interactions modify this dependence and for moderate interaction strength the current is found to be independent

We study the possibility of suppressing light shifts in Ramsey spectroscopy of coherent population trapping (CPT) using generalised autobalanced Ramsey spectroscopy (GABRS) and combined error signal in Ramsey spectroscopy (CESRS). We consider CPT resonances excited by a coherent bichromatic field in an open Λ-system with a 'trap' state. Using a rigorous mathematical proof and numerical calculations

The lifetime of a gas of 6Li atoms in a large hollow optical dipole trap formed by radiation with a frequency detuned by 4 or 2 GHz upward from resonance is measured. The trap has the shape of a thin-walled cylinder with flat bases and a volume of ≈1 mm3. The main mechanism responsible for the loss of atoms is heating due to Rayleigh scattering. The influence of collisions of atoms with the background

We have assessed the effect of optical lattice laser field parameters (polarisation, intensity, and wavelength) of a coldytterbium atomic frequency standard on the systematic uncertainty of precision clock transition frequency measurements. The spectrum and polarisation of the laser field of the lattice have been investigated in detail directly in the spatial region of interaction of cold ytterbium

A scheme is proposed for the third stage of laser cooling of thulium atoms at a wavelength of 506.2 nm, and a system for stabilising the laser radiation frequency is described, which provides the required characteristics. The transition |4f13(2Fo)6s2, J = 7/2〉 → |4f13 (2F o 7/2 6s6p, J = 9/2〉 at a wavelength of 506.2 nm is detected in a magneto-optical trap with the employment of the developed laser

We report recent results on the development of an optical frequency standard based on the quadrupole transition in a single 171Yb+ ion. The probe laser frequency is simultaneously stabilised to the transmission peak of a Fabry–Perot reference cavity and the central resonance of the quadrupole transition of the ion with a linewidth of 30 Hz. With the experimentally obtained spectral characteristics

We report the results of experiments on implementing individually addressable one-qubit quantum gates on a microwave transition with two 87Rb atoms in two optical dipole traps. Addressing is carried out using additional focused laser light, which results in a differential light shift of the microwave transition frequency. In the absence of addressing in each of the atoms, Rabi oscillations are obtained

Quantum technologies are one of the highest priority areas of research in the 2020s. The Russian government has supported a wide range of works in the areas of such roadmaps as 'Quantum Computing', 'Quantum Communications', and 'Quantum Sensors', aimed both at reducing the gap with world leaders and at achieving new frontiers in the field of basic and applied physics. At the same time, quantum technologies

A scheme is proposed for processing optical signals in a receiver of a communication system, based on complex fully connected neural networks. The influence of the main characteristics of the neural network on the efficiency of nonlinear distortion compensation is studied. A significant advantage of the proposed scheme over real-valued neural networks is demonstrated.

For further development of the comparison method, the X-ray spectra of laser plasmas of light (Si, S, Cl, K, Ca, Ti) and heavy (Mo, W) elements are studied. Plasma is produced by focusing nanosecond laser radiation (λ = 0.53 μm, E L = 5 J, τ = 2 ns) onto massive solid targets. The spectra are recorded using two focusing crystal spectrometers in the wavelength range λ = 2 – 11 . A detailed analysis

An analytical model has been developed for the generation of a superstrong quasi-stationary magnetic field (up to several GG) in the focal waist of an ultra-intense short circularly polarised laser pulse interacting with a gas-cluster target. The rotation of relativistic electrons around the ionised core of the cluster has been shown to produce a magnetic moment and a quasi-stationary magnetic field

High-efficiency harmonic generation is observed in a semiconducting polymer RR-P3HT [regioregular poly(3-hexylthiophene)], which exhibits a high nonlinear susceptibility [χ (2) > 10−6 m V−1] under pumping by a pulsed fibre laser. The harmonic generation efficiency in RR-P3HT is comparable or higher than that observed for liquid crystals, which are used in reference experiments to estimate the susceptibility

A method is proposed for enhancing the time-domain contrast of femtosecond laser pulses under nonlinear pulse compression by means of spectrum broadening due to the self-phase modulation with a following reflection from chirped mirrors. The contrast increases because the radiation of the pedestal is blocked by a square screen arranged in a focal plane of a unit-magnification telescope, and the main

This paper describes experiments concerned with pulse train generation from initially modulated cw light in an anomalous dispersion decreasing fibre. We have obtained stable contrast trains of subpicosecond pulses with a repetition rate in the range 100 – 300 GHz and demonstrated generation of an optical comb spectrum with a –20-dB width of up to 80 nm. A method has been proposed for reconstructing

An AlGaAs laser (907 nm, 0.2 μJ) with a 3-ns pulse duration and eye-safe energy density below 1 μJ cm−2 is developed for lidar application. The laser is composed of three stacked diodes in a plastic housing. An external pump current generator based on discrete elements with an FMMT417 bipolar transistor switch is assembled on a printed circuit board together with the laser. A lidar based on this laser

We have demonstrated stable Q-switched mode-locked operation of an in-band pumped Ho : Y2O3 ceramic laser at 2117 nm by using an InGaAs/GaAs-based saturable absorber. An average output power of 330 mW is reached for 2.7 W of absorbed pump power with stable mode-locked pulses having a 98.9-MHz repetition rate and 100% modulation depth embedded inside Q-switched envelopes of ∼1.7-μs duration. The duration

Lasing in caesium vapour is obtained at λ ∼ 3 μm (transitions 7P3/2 → 7S1/2 and 7P1/2 → 7S1/2). Longitudinal pumping is performed by the second harmonic of a parametric oscillator pumped by the second harmonic of a Nd3+-doped garnet laser. The pump wavelength corresponds to the 6S1/2 → 7P3/2 and 6S1/2 → 7P1/2 transitions of caesium atoms. The pump radiation has a spectral width of 12 cm−1, a pulse

Simulation of light propagation by the statistical Monte Carlo (MC) method is widely used in many fields, especially in astrophysics, atmospheric optics, ocean optics, and nuclear medicine. In the optics of biological tissues, the MC method is used to simulate the luminous flux, which is formed during various medical therapeutic or diagnostic procedures inside a biological tissue and on its surface

We propose to solve the inverse problem of diffuse fluorescence tomography (DFT) – reconstruction of the spatial distribution of the fluorophore in biological tissues – by a method based on Tikhonov regularisation with the nonnegativity condition (TRNC) of the reconstructed components of the solution vector. Model experiments on a biotissue phantom demonstrate that the TRNC method allows for a more

Vacuum UV radiation from laser-induced plasma is used to ionise volatile organic compounds (VOCs) released by living organisms during their mass spectrometric analysis at atmospheric pressure without sample preparation. It is shown that the probability of ionisation of organic compounds with different ionisation potentials and proton affinity at atmospheric pressure in the argon flow weakly depends

A Raman spectrometer for gaseous media with a detection limit at a level of 100 ppb is developed. The results of its experimental approval on exhaled air samples from healthy people confirmed the possibility of monitoring the concentrations of a number of hydrocarbon compounds and 13CO2. The ways of further development of this analytical method are outlined.

Spherical ultrasonic antennas are used in raster-scan optoacoustic (OA) angiography to record broadband signals generated by haemoglobin molecules in blood when they absorb pulsed optical radiation. Depending on the size of haemoglobin-containing structures, the characteristic frequencies of OA signals can vary quite significantly, ranging from hundreds of kilohertz to hundreds of megahertz. Meanwhile

We report a theoretical and experimental study of the excess photocurrent noise in the detection of low-coherence radiation caused by the beats of the random components of the optical spectrum at equal intensities in the interferometer arms. It is shown that, in this case, the spectral density of photocurrent fluctuations is times higher than when detecting radiation without interference. This result

The problem of recognising single sparsely located scatterers against the noise background in the image obtained by the method of optical coherence tomography (OCT) is considered. An identification method based on the use of specific scanning features upon OCT image registration and on the statistical analysis of image fragments is proposed. The efficiency of the method is demonstrated experimentally

We have studied luminescent properties of a ZnO whisker array, a promising crystalline material for scintillation detectors, capable of ensuring a fast and strong response and a short afterglow time. Measurements have been performed under X-ray and UV optical excitation. We present a comparative analysis of spectral features of the near-band-edge emission of the whisker array at low (∼80 K) and room

We report the results of measuring the complex coupling coefficients in ring He – Ne lasers with a radiation wavelength of 632.8 nm. It is found that in assembling ring resonators from mirrors of the same quality, there is no correlation between the dissipative and conservative backscattering components. The analysis of the measurement results shows that this behaviour is associated with the speckle

We consider the issues of measuring the deformability of red blood cells by the method of laser diffractometry in shear flow (ektacytometry). The measurement procedure is optimised taking into account the finite resolution of the video recording system of the laser ektacytometer. An algorithm is proposed that allows one to determine with high accuracy the diffraction pattern parameters necessary for

Two-dimensional optical image edge enhancement is investigated using a spatial acousto-optical (AO) filter operating at two wavelengths of optical radiation, which significantly increases the reliability of measurements and also reduces the effect of noise. The filter operates basing on diffraction of light in two diffraction orders. It is shown that, in the general case, it is impossible to obtain

A configuration of a laser polarisation modulator based on isotropic acousto-optic interaction is proposed. Polarisation control is performed by a 2D acousto-optic cell based on one monoclinic single crystal. A possibility of implementing this modulator on the basis of a KY(WO4)2 crystal is demonstrated.

A method for obtaining non-Gaussian light beams with azimuthal field polarisation in a waveguide quasi-optical cavity is described. The method is based on the employment of polarisation-selective diffraction structures as laser mirrors. Efficient excitation of such beams at the output from an optically pumped waveguide HCOOH laser (λ = 0.4326 mm) with an inhomogeneous reflecting input and semitransparent

Indirect drive thermonuclear targets with fuel capsules at the stage of X-ray irradiation in a free flight are proposed. The absence of structural elements fixing the fuel capsule at the beginning of this stage will make the initiation of their associated instabilities impossible and will thereby improve the fuel compression.

Generation of coherent radiation in the IR and terahertz ranges during the propagation of a multi-terawatt laser pulse along a nanowire target is investigated. In the process of interaction, dense electron bunches are displaced from the target and accelerated in the laser field, generating intense electromagnetic radiation. Three regimes of interaction can be realised depending on the duration and

Nanosecond laser ablation of a bulk gold target in a melt of a sodium nitrate salt is investigated. It is shown that the form of plasma plumes on the target surface during ablation depends on the laser beam scan rate. The extinction spectra of sodium nitrate composites with gold nanoparticles during solidification is analysed.

The selectivity of laser photoionisation of 177mLu nuclear isomer with respect to natural isotopes has been studied for the first time using a three-stage lutetium photoionisation scheme .

We report a study of the effect of postgrowth treatment of ZnGeP2 single crystals (low-temperature annealing, irradiation with fast electrons, polishing of working surfaces) and the conditions of exposure to repetitively pulsed laser radiation [wavelength (2091 or 1064 nm), pulse repetition rate, beam diameter, exposure time, sample temperature] on the laser-induced damage threshold (LIDT) of the surfaces

Using an improved travelling wave model, we have numerically investigated the dynamics of a Q-switched bismuth-doped fibre laser. Comparison of simulation results with previously reported experimental data demonstrates good agreement of the multipeak lasing structure and the shape of the strongest pulses at various levels of pumping. We have assessed the effect of the main laser parameters on output

We study the conditions of frequency modulation, spectral broadening, and amplification of a Gaussian pulse – a whispering-gallery-mode (WGM) wave packet (WP) – propagating along a spiral trajectory on the surface of an active cylindrical optical waveguide, in which a travelling refractive-index wave (TRIW) is generated. Analytical expressions are obtained for the dependences of the duration, chirp

Operation of a tunable tandem-type low-coherence light source with high spectral brightness based on commercially available optical elements (superluminescent diode, semiconductor optical amplifier, and bulk dwiffraction grating) is studied experimentally. A unique combination of the output source characteristics, namely, a spectral power density of 36 mW nm−1, a wavelength tuning range of 35 nm (834

Semiconductor lasers based on AlGaInAs/InP heterostructures with ultra-narrow and asymmetric waveguides are comparatively studied. It is shown that the use of these waveguides with a simultaneous increase in the quantum well depth makes it possible to increase output powers. Such lasers based on both strongly asymmetric and ultra-narrow waveguides with a stripe contact width of 100 μm demonstrate an

We report the results of theoretical and experimental studies of a digital system for regulating and stabilising the frequency of a four-frequency Zeeman laser gyroscope (ZLG), in which generation occurs simultaneously on two longitudinal modes with orthogonal circular polarisations; therefore, four light waves propagate in the optical ring resonator. In contrast to a two-frequency Zeeman laser gyroscope

A high degree of cross-correlation of radiation wavefront aberrations, measured from a point reference source and from an extended object (a system of several luminous points), has been for the first time revealed based on simultaneous measurements of phase fluctuations in optical waves propagating in a turbulent atmosphere. The experimental data are consistent with analytical calculations. The high

We have developed and experimentally implemented an adaptive laser vector-phase hydroacoustic measuring system, which allows one to determine the total acoustic intensity vector. A receiving element of the measuring system comprises six spatially separated fibre-optic coil-type sensors. Signals from the sensors are phase demodulated by using a six-channel adaptive holographic interferometer based on

We report the results of theoretical and experimental studies of noise in a delay-line optoelectronic microwave oscillator with optical gain. The effect of various noise sources on the parameters of an optoelectronic microwave oscillator is considered, and, in addition to the noise of its individual components, several linear and nonlinear mechanisms for converting optical carrier noise into microwave

We present the design and results of studying the characteristics of an optoelectronic microwave oscillator in the free-running regime are presented, propose a method for synchronising it with a signal of a highly stable crystal oscillator using a phase-locked loop, and analyse the results of an experimental study on the frequency instability of an optoelectronic microwave reference oscillator. The

We report a theoretical analysis of the spectral properties of atoms localised in an optical pulsed trap. It is shown that this analysis can be carried out using the correlation coefficient calculated from the averaged dynamics of atomic excitation by resonant probe laser light in the presence of a nonresonant pulsed field. It follows from calculations that at a laser pulse duration of 8 ps, atoms

We have proposed a new design of microstructured optical fibres (MOFs), containing three rings of identical circular holes around a core, with different separations between the rings. The properties of the MOFs have been analysed numerically using the finite element method (FEM), and the leakage loss in the spectral range 0.40 – 2.65 μm has been calculated for the fundamental and higher order modes

The results of spectral diagnostics of an optical discharge (OD) plasma propagating through a hollow-core revolver fibre under the action of repetitively pulsed laser radiation are presented. The revolver fibre is made of silica glass, with a diameter of the hollow core being 20 μm. The peak values of the laser radiation intensity reach 1012 W cm−2at an average Nd : YAG laser power of about 2 W. The

To raise the stimulated Brillouin scattering (SBS) threshold, we have fabricated an optical fibre having a core heavily doped with germanium oxide and displaced from the fibre axis. A method has been proposed for broadening the SBS gain spectrum of the fibre by winding it onto a small-diameter spool, and a broadening of the spectrum by 5.4 dB has been demonstrated, which indicates an increase in SBS

We describe an experiment on the interaction of a dipolar magnetic field with the laser plasma flow produced inside of a laboratory magnetosphere. This interaction is found to exhibit two dynamic stages: after a prompt displacement of the dipole field by the laser plasma, the magnetic field is captured and carried outside of the magnetosphere. The resultant data confirm the results of previous measurements

The SRS process in the regime of nonlinear phase modulation of laser and Stokes radiation waves is studied experimentally. The effect of the relationship between the laser and Stokes wavelengths on the value of the minimum laser pulse duration, at which an efficient SRS process is possible, is ascertained. The possibility of obtaining maximally broadband Stokes radiation pulses by matching the group