Table of contents

Results obtained at the first stage of development of the experimental technique for obtaining weight amounts of the highly enriched ¹⁵⁰Nd isotope by laser photoionisation are presented. The vaporiser and the laser are designed, and various methods of irradiation of neodymium vapour and extraction of photoions are tested. The product yield ∼40 mg h^-1 for the ∼60% enrichment and 25 mg h^-1 for the ∼65% enrichment is achieved for a vaporiser of length 27 cm. The cost of constructing the facility for preparing 50 kg of the ¹⁵⁰Nd isotope, intended for determining the neutrino mass, is estimated. This estimate shows that the cost of production can be lowered by a factor of 5–7 compared to the electromagnetic method.

The analytic solution of the problem of spontaneous decay of an atom near a cluster of two perfectly conducting nanospheres is found. It is shown that spontaneous decay rates can considerably decrease or increase depending on the system geometry. In particular, within the framework of our model, the decay rate of an atom located between closely spaced spheres and having the transition dipole moment directed along the symmetry axis can be arbitrarily high.

Expressions for the frequency shift of radiation of an atom located near a cluster of two perfectly conducting spherical nanoparticles are obtained within the framework of a classical model. The asymptotic expression is found for the radiation frequency shift of an atom located between spheres approaching each other.

It is shown that if a supersonic oxygen—iodine ejector laser is fed by singlet oxygen from a centrifugal bubbling generator operating at a centrifugal acceleration of ∼400g, the laser output power achieves a value 1264 W at a chemical efficiency of 24.6% for an alkaline hydrogen peroxide flow rate of 208 cm³s^-1 and a specific chlorine load of 1.34 mmol s^-1 per square centimetre of the bubble layer.

To improve the parameters of laser diodes emitting in the 1000–1070-nm spectral range and develop highly efficient laser diodes emitting in the 1070–1100-nm range, it is proposed to introduce GaAsP barrier layers into the active region of the quantum-well InGaAs/AlGaAs heterostructure, which compensate for enhanced mechanical stresses. This considerably improves the luminescence characteristics of heterostructures and changes conditions for generating misfit dislocations. The long-wavelength lasing at 1100 nm becomes possible due to an increase in the thickness of quantum wells and in the molar fraction of InAs in them. The manufactured laser diodes emitting in the 1095–1100-nm range have low threshold currents, the high output power and high reliability.

The peculiarities of parametric optimisation of resonators containing small-scale inhomogeneities are considered. The two most important practical cases are studied in detail: an unstable resonator with small-scale phase inhomogeneities in the active medium and a stable resonator with small-scale amplitude modulations caused by the use of a perforated output mirror.

Propagation of light in a cylindrical system of tunnel-coupled waveguides is studied. The waveguide system was constructed by layer-by-layer deposition of waveguides on the inner wall of a reference tube by the SPCVD technique developed for synthesising fibre preforms. It is shown that the waveguide light beam in such a system moves along a helical wave-like trajectory and is partially emitted outside at its 'crests'. The angular dependence of the trajectory period and of the number of oscillations along the trajectory is measured.

The formation of optical waveguide channels is experimentally demonstrated upon the photorefractive self-action of a phased light beam in a planar waveguide optically induced in an iron-doped lithium niobate crystal. Planar and channel waveguides were produced by using a 633-nm He—Ne laser with output powers 1 mW and ∼10 μW, respectively.

The concept of generalised quantum measurement is introduced as a transformation establishing the correspondence between the initial state of an object and the final state of the object—instrument system with the help of a classical information index one-to-one related to a classically compatible set of the states of the object—instrument system. It is shown that this measurement includes all the types of measurements: standard projective, entangling, soft, and generalised measurements with a partial or complete dest-ruction of the initial information contained in the object. A special class of partially destructing measurements is considered which establish the correspondence between a continual set of states of finite-dimensional quantum systems and systems with an infinite-dimensional space of states. The information sense of these measurements is discussed and some information characteristics are calculated.

The dynamics of dark solitons is studied within the framework of the mathematical model of nonlinear Schrödinger equation (NSE) with an external harmonic potential. A comparative analysis of the solutions of nonstationary problems is performed for a linear harmonic oscillator and the NSE model with a harmonic potential for different signs of the self-action potential. It is shown that the main specific feature of the dynamics of dark NSE solitons in a parabolic trap is the formation of solitons with dynamically changing form factors producing the periodic variation in the modulation depth (the degree of 'blackness') of dark solitons. The oscillation period of the dark soliton does not coincide with the oscillation period of a linear quantum-mechanical oscillator, which is caused by the periodic transformation of the black soliton to the grey one and vice versa. The conditions of applicability of the method of inverse scattering problem are presented, the generalised Lax pair is found, and exact soliton solutions are given for the mathematical NSE model with an external harmonic potential.

The relation between the phase and amplitude components of an inverse population grating in a Nd:YAlO₃ crystal is studied for different polarisations of probe radiation and under different conditions of flashlamp pumping. It is shown that temperature refractive-index gratings play a significant role in degenerate multiwave interactions in a saturated laser medium.

Periodic microstructures — ripples oriented perpendicular to the direction of radiation polarisation are produced by irradiating crystalline silicon with the (100) orientation of the surface by femtosecond laser pulses. The behaviour of the third-harmonic signal is studied in these microstructures. It is shown that the orientation dependences of the third-harmonic signal for optically induced ripples are determined by the morphology of the latter on the irradiated silicon surface, which allows the in situ diagnostics of these microstructures.

The dynamics of a high-power femtosecond tubular pulsed beam in a dielectric medium is numerically analysed upon optically induced ionisation. It is found that the balance between nonlinearities of opposite sign and different magnitude in the case of multiphoton ionisation favours the establishment of a quasi-soliton regime of radiation propagation over a distance exceeding several diffraction lengths. The use of these beams enables attaining high-density light fields and generate high-density plasmas.

The impurity layer on the surface of a solid target is shown to exert a significant effect on the characteristics of the ion current of the laser plasma produced under the action of ultrahigh-intensity femtosecond radiation on the surface of this target. The application of pulsed laser cleaning gives rise to an additional high-energy component in the ion spectrum of the target material. It is shown that the ion current parameters of the laser plasma such as the average and highest ion charge, the highest ion energy of the target material, etc., can be controlled by varying the lead time of the cleaning laser radiation.

The appearance of the potential difference is observed on electrodes placed in a cell with water irradiated by a Q-switched 2.92-μm Cr³⁺:Yb³⁺:Ho³⁺:YSGG laser.

The relative intensity noise (RIN) and small-signal intensity modulation (IM) of a hybrid soliton pulsed source (HSPS) with a linearly chirped Gaussian apodised fibre Bragg grating (FBG) are considered in the electric-field approximation. The HSPS is described by solving the dynamic coupled-mode equations. It is shown that consideration of the carrier density noise in the HSPS in addition to the spontaneous noise is necessary to analyse accurately noise in the mode-locked HSPS. It is also shown that the resonance peak spectral splitting (RPSS) of the IM near the frequency inverse to the round-trip time of light in the external cavity can be eliminated by selecting an appropriate linear chirp rate in the Gaussian apodised FBG.

It is shown experimentally that when phase conjugation (PC) methods are used for self-directing laser radiation to remote objects, the fraction of laser radiation hitting the object amounts to 80%±10% of the total energy reflected from a PC mirror, and in most cases depends weakly on the degree of atmosphere turbulence and the path length despite considerable aperture losses.