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Experimental parameters of the resonance of coherent population trapping (CTP) on D1 line in 87Rb and light shifts are compared under modulation of the laser pump current at frequencies of 3.4 and 6.8 GHz. Reproducibility of the parameters of a laser with a vertical cavity needed for long-term stability of an atomic clock is considered. The instabilities of atomic CPT-clock obtained for 1 s are 1.2 × 10−11 and 3 × 10−12 for frequencies of 3.4 GHz and 6.8 GHz, respectively.

Inscription of structures by a femtosecond laser beam allows one to produce disordered structures capable of increasing the Rayleigh backscatter intensity in the fibre at relatively low induced losses, which makes them potential candidates for use as reflectors in fibre lasers. Here we report a narrow-band erbium fibre laser with random distributed feedback produced by femtosecond laser writing in half-open cavity and ring cavity configurations. In the half-open cavity configuration, single-frequency lasing is observed at output powers up to 2.8 W, with a linewidth near 10 kHz. In the ring cavity configuration, single-frequency operation is observed over the entire range of output powers studied. At the highest output power, 7 mW, the linewidth does not exceed 0.7 kHz.

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 D1 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 shown that in this configuration, the hypercontrast effect can be observed for sub-Doppler resonances, which makes this configuration promising for the employment in new-generation miniature optical frequency standards. In the present work, two different two-frequency configurations are compared with each other and with the single-frequency configuration widely used in practice for observing saturated absorption resonances. The parameters of nonlinear resonances are measured at various temperatures of caesium vapours and at different optical field intensities. The results of the investigations performed make it possible to find an optimal two-frequency scheme for exciting nonlinear resonances and to estimate a potential of the scheme for its applications in quantum metrology.

We report the results of the development and production of a quantum frequency standard (QFS) based on the coherent population trapping (CPT) resonance observed on the D1 absorption line of 87Rb atoms. The effect of various physical factors on the QFS frequency is studied, and the optimal physical parameters of the device to attain the best frequency stability are determined. The measured relative frequency instability (Allan deviation) is ∼9 × 10−12 for the averaging time of 1 s, 3 ×10−13 for 1000 s, and 1.5 ×10−12 for 24 hours. For a volume of 60 cm3, the power consumption of the entire device is 300 mW. The designed QFS can be used in a new-generation satellite navigation systems with increased accuracy and reliability, as well as for solving a number of other problems of science and technology.

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 of the reduction in nonlinear effects owing to the larger effective mode area in the multicore fibre in comparison with a standard single-mode fibre Raman laser.

Results of high-precision frequency measurements are presented for certain components of the 127I2 hyperfine structure, which correspond to emission transitions of the B – X band in the range of 1053 – 1068 nm. The frequencies are measured by using a femtosecond optical frequency synthesiser based on a Ti:sapphire laser. The hyperfine structure is resolved by the method of three-level laser spectroscopy. The frequency-doubled cw Nd : YAG laser is used as an excitation radiation source, and the probe radiation in the range of 1050 – 1070 nm is generated by an external-cavity diode laser. The frequencies of both lasers are simultaneously locked to those of two adjacent hyperfine structure components of iodine lines, which have a common upper level. Correspondingly, the frequency of the Nd : YAG laser is locked to the frequency of the absorption transition component, and the diode laser frequency – to the frequency of the emission transition component. The radiation frequency of the diode laser ‘locked’ in this way is measured. Frequencies of 18 hyperfine structure components for six emission lines corresponding to the bands (32 – 54) and (32 – 53) are measured. The relative uncertainty of the measurement is 8 × 10–10.

Using a point-by-point fs inscription technology, a Rayleigh reflector with unique characteristics has been designed and fabricated. The reflection coefficient of the structure with a length of 5 cm amounts to 0,03%, which corresponds to the reflection of 6-km SMF-28e+ fiber spool. The designed artificial Rayleigh scattering fiber in combination with distributed feedback (DFB) erbium-doped fiber laser allows to narrow the linewidth. A similar effect was observed in configuration with 25-km SMF-28e+ fiber spool, where it was used as an additional spectral filter. In both cases, an identical narrowing of the linewidth by an order of magnitude was observed at times less than 0,1 msec.

Environmental safety issues are becoming increasingly important in the life of society. Among environmental safety issues in power engineering, acoustic safety occupies a special place. The problem of acoustic safety is associated with the fact that the regular operation of power equipment leads to an increased noise level, and power facilities are located in close proximity to residential areas. In this work, acoustic calculations were performed to determine the sanitary protection zone for gas turbines units (GTU) and combined cycle gas turbine units (CCGT) of various capacities. A formula was obtained for calculating the width of the sanitary protection zone depending on the capacity of gas turbine units and combined cycle plants and their number. It is shown that the sanitary protection zone (SPZ) of a power unit of high capacity is smaller than the sanitary protection zone of several power units of the same capacity. It is found that the noise levels from individual groups of equipment can determine the noise level at the entire border of the sanitary protection zone or in its individual sections. At the same time, noise suppression measures should be taken for all sources that generate noise levels in excess of standards. It is necessary to start noise suppression measures from those sources that generate excess noise in a larger section of the sanitary protection zone.

The introduction of precision farming technologies at agricultural organizations in Russia is proceeding at a slow pace, that makes it necessary to find ways to intensify this activity. The study aims to identify opportunities, threats, strengths and weaknesses and develop scientific and practical recommendations on strengthening the use of precision farming technologies in agriculture. Agricultural experts were involved in assessing these characteristics. The strengths include raising awareness of agricultural managers and specialists about the progress in work performed (the conditional index is 4.13 points) and reducing the consumption of material resources (3.83 points). The introduction of these technologies is encouraged with the availability of the Internet at rural areas (3.56 points). The greatest concern is about the functional and physical depreciation of the material and technical base (3.98 points) and insufficient government support (3.44 points). It is necessary to develop governmental targeted measures on increasing state support for updating the material and technical base of agriculture, restoring the human capital in the industry, and developing technologies for precision farming of domestic (Russian) production, which will reduce the dependence on exchange rate fluctuations.

The article discusses the problems of changing the essence of work of agricultural workers in the context of introduction of digital technologies. The research aims to study the changes in heaviness and intensity of work of agricultural workers as a result of introduction of digital technologies. As research methods, the workplace of a robotic milking operator was assessed in comparison with a machine milking operator. And 7 indicators belong to class 1 and 6 indicators to the second class of the working conditions, therefore, a general assessment of work heaviness corresponds to the class “Acceptable” (class 2). The assessment of work intensity revealed 7 indicators that belong to class 3.1 (stressful work of the first degree) and 3 indicators to class 3.2 (stressful work of the second degree). This allows making a conclusion that a general assessment of work intensity of a robotic milking operator corresponds to the class of stressful work of second degree. The use of robotic milking can be recommended to reduce the loads for livestock workers. At the same time, attention should be paid to reducing the work intensity of robotic milking operators.

The researches were conductedon queen bees of the Carpathian subspecies in conditions of Tajikistan. Four groups of similar families were formed, 10 in each group. In the control group, sugar syrup (1:2) was given as a stimulating feeding, in small portions of 700 ml. Bees of the first experimental group were fed with the sugar syrup, with the addition of drone larvas’ homogenate. The second group was fed with the sugar syrup with addition of a feed mixture “Similak”, the third group - sugar syrup with the addition of a compositional form consisting of a feed mixture “Similak” and the drone larvas’ homogenate. In the experimental groups, in contrast to the control group, an increase in the egg production of queen bees and the brood breeding reflex by 1.3-1.44 times was found.In general, it has been established that to stimulate the physiological processes in bee’ organism, growth and development of colonies in spring, it is necessary to use stimulating feeding by sugar syrup in combination with drone larvas’ homogenate and feed mixture “Similak” 700 ml each.

In the paper presents results of an experimental comparison of the CPT parameters of the resonance at the D1 line in 87Rb when the laser current is modulated at frequencies 3.4 GHz and 6.8 GHz. Resonances are investigated for slope to noise ratio (Q-factor) and shifts from the microwave power. The reproducibility of the parameters of VCSEL lasers required to obtain long-term stability of an atomic clock is considered. The obtained CPT instabilities of the atomic clock for 1 second were 1.2·10−11 for the case of 3.4 GHz and 4·10−12 for 6.8 GHz.