The results of measuring the derivative of the pulse wave using a laser autodyne based on the Fourier analysis of the low-frequency 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 the frequency dependence of the windowed Fourier transform obtained from the analysis of the interference signal is calculated. It is shown that the amplitude of biovibration of the skin surface has the greatest influence on the correlation of the frequencies of the window spectrum of the autodyne signal with direct measurements of the pulse wave parameters by the sphygmographic method. Using a hardware-software system, we measured the sphygmogram of the pulse wave in the radial artery in a 19-year-old man who did not suffer from cardiovascular diseases. The derivative of the pulse wave obtained from the sphygmogram was compared with the dependence of the frequencies of the window spectrum of the autodyne signal. A comparative analysis of the dependences of the frequencies of the spectral harmonics of the window method with the derivative of the sphygmographic pulse showed a good correlation at the amplitudes of biovibration of the skin surface exceeding 10 μm.

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.

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 tissue matrix modified at temperatures below the denaturation threshold is observed in images obtained by nonlinear optical microscopy in the regime of second harmonic generation. The modification has specific features under long-duration (with a duration longer than 1 s) and short-duration (10 – 30 ms) action: separation of a fibre bundle into groups with distorted passage in the first case and bundle splitting to chaotically directed fibres in the second case. The character of the tissue change determines the coefficient of organic substance diffusion into a tissue material. After matrix amorphisation (collagen denaturation) or distortion of the fibre group arrangement in the collagen bundle, the diffusion coefficient falls by 10 % – 40 %, whereas after bundle splitting it increases by 25 % – 50 % as compared to the value of (3 ± 0.1) × 10−6 cm s−1, which is specific for intact tissue. The results obtained make us to assume that the specific disordering of the tissue collagen framework under the short-duration action may be used for increasing the permeability of the scleral tissue.

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 on the coupling constants. Particular solutions of a system of coupled waves are found, which describe strongly localised light propagating without transverse diffraction along the entire lattice at certain values of the coupling constants. The emergence of spatially limited transverse diffraction of light is predicted.

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 rate, as well as the correct allowance for the noise of the CCD camera when calculating the Strehl ratio are investigated.

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 acousto-optic (AO) interaction upon double passage of two-colour radiation through an AO cell made of a gyrotropic crystal; the method efficiency is demonstrated by the example of radiation from an Ar laser generating at wavelengths of 0.488 and 0.514 μm and an AO cell made of TeO2, operating at a sound frequency of 60 MHz.

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 experimental data. The origin of the observed quantitative discrepancies is discussed.

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 form of gamma distribution and the Gaussian function is substantiated. It is shown that the specific form of these functions is determined both by the mean value (mathematical expectation) of the interference signal and by the characteristic parameter M, which depends on the statistical properties of the laser interference.

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-to-noise ratios is investigated taking into account the parameters of real multi-element photodetectors (MEPDs). The obtained results indicate the possibility of evaluating relief signatures of distant objects with high accuracy based on standard MEPDs simultaneously for a large number of points on the object’s surface with a signal-to-noise ratio of more than 4.

The luminescence of Xe2Cl* excimer upon optical excitation of high-pressure Cl2 – Xe mixtures by XeCl laser pulses (λ = 308 nm) with different energies is investigated. It is shown that small-signal gain of the Xe2Cl amplifier may reach ∼1.3 × 10−1 cm−1 in a mixture of Cl2 and Xe with partial pressures of 4 Torr and 9 atm, respectively, and an excitation fluence of 1026 photons cm−2 s−1.