High-order harmonics generation (HHG) driven by the femtosecond multi-band laser system, based on Cr:Forsterite (1.24 um) and Fe:ZnSe (4.5 um) crystals, has been realized in an argon gas jet. The assessed vacuum intensity at the target region is at the level of $10^{14}-10^{15} \mathrm{~W} / \mathrm{cm}^{2}$, corresponding Keldysh parameter is at the level of 0.2, that indicates the tunneling regime of ionization. The measured harmonics orders are in the range of 43-71 eV with total generated photon number at the level of $5 \times 10^{8}$ photons per pulse, energy of 4.4 nJ and corresponding conversion efficiency of $3 \times 10^{-6}$. It is experimentally established, that the increase of gas jet pressure leads to blue-shifting and double-peaking in harmonics spectrum due to the nonlinear propagation effects of generating radiation. The effective generation of THz radiation by the 1.24 -um laser pulses of Cr:Forsterite laser system and extension of the generation wavelength to the mid-IR (4.5 um) range by driving of Fe:ZnSe laser system pave the way toward the HHG generation by near- and mid-IR radiation in the presence of strong THz field.

The generation of terahertz radiation in a BNA crystal pumped by 1.24-µm femtosecond laser radiation from a Cr:forsterite laser system with a pulse duration of 100 and 35 fs and a pump density of 10 mJ/cm 2 has been realized. The achieved generation efficiency is 0.1%. It is found that a decrease in the pump pulse duration from 100 to 35 fs leads to the generation of high-frequency components in the ranges of 2.5–6.5 THz and 9‒10.5 THz in the generated radiation spectrum. Simulation of the terahertz radiation generation based on the solution of Maxwell’s equations by the finite-difference time-domain method has made it possible to adequately describe the measured spectra. The generation of broadband high-frequency terahertz radiation in the BNA crystal pumped by the Cr:forsterite laser system allows one to consider this schematic as an alternative to sources based on the BNA crystal pumped by a Ti:sapphire laser system.

One of the promising trends in modern agronomy is the development of automated closed urban vertical farms with controlled environmental conditions, which can improve dynamics of the crop vegetation process. In the frame of this work, the analysis of the vegetative stages of potato seed material (minitubers and microplants) grown in the conditions of the automated vertical farm was conducted. The study was performed at the vertical farm of the Federal Research Center “Fundamentals of Biotechnology” of the Russian Academy of Sciences by the analysis of water consumption dynamics. It was established that the 20-day reduction in the vegetative period of the vertical-farm-grown potatoes in comparison with the field-grown ones occurred due to the reduction in the final stage of vegetation (mass gain of newly formed tubers) under the minitubers planting. The same reduction occurred due to both final and initial vegetative stage (absence of tubers germination) under the planting of microplants. The obtained result shed new light on the vegetation dynamics of potato grown under controlled conditions of the urban vertical farms and demonstrated a possibility to perform the study of plant development process using automated diagnostics systems of vertical farms.

The effect of the length and pressure of an argon gas jet on low-order harmonics (5th, 7th, 9th, and 11th) generation by 4.5-μm femtosecond laser radiation of a Fe:ZnSe laser system has been studied experimentally. It has been shown that an increase in the length of the generation medium up to the waist length allows one to increase the generation efficiency by a factor of 12. It has also been demonstrated that a change in the length of the gas medium changes the pressure dependence of the energy of the generated radiation because of change in the phase matching conditions, whose correct simulation requires the inclusion of nonlinear propagation effects for pump pulse and generated harmonics.

Urban vertical farming is an innovative solution to address the increasing demand for food in densely populated cities. With advanced technology and precise monitoring, closed urban vertical farms can optimize growing conditions for plants, resulting in higher yields and improved crop quality. However, to fully optimize closed urban vertical farming systems, research is needed to enhance crop yields and reduce the growing season. The present study is focused on the research of the mutual influence of microclimate parameters, such as temperature, humidity, and carbon dioxide concentration, as well as the spectral composition of light, humidity, and amount of peat in the substrate. The research was conducted within the cultivation of the "Innovator" potato variety at the experimental automated vertical farm of the "Fundamentals of Biotechnology" of the Russian Academy of Sciences. Based on the correlation and Fourier analysis of the dependences of soil moisture and carbon dioxide concentration on time, it is shown that after watering potatoes, there is a 56 h delayed decrease in the concentration of carbon dioxide in the cultivation room, which can be explained by a delayed increase in the intensity of the photosynthesis process. Moreover, a comparison of CO2 dependence on time with the lighting dynamics at the scale of one day indicates the presence of the intrinsic daily biological rhythm of the CO(2 )absorption rate that does not depend on the external lighting conditions. In addition, by analyzing the dependencies of microclimate parameters and the spectral composition of the lighting over time, it was found that switching on lighting influences the microclimate parameters, which can be explained by the heating of LEDs used for lighting. Moreover, the multiple regression analysis of microclimate parameters and soil moisture showed that an increase in peat content in the substrate leads to a transition from the decisive influence of air humidity on soil moisture to the dominant influence of air temperature. The obtained results reveal the complex mutual influence of the parameters determining the growing conditions within automated closed vertical farms. Consideration of this influence is necessary when optimizing the conditions of vegetation and the development of intelligent plant-growing systems.

It has been shown that the spectrum of intense few-cycle terahertz radiation generated in a DAST organic crystal can be controlled by chirping 1.24-μm pump femtosecond laser radiation of a chromium forsterite laser system. It has been found that an increase in the linear chirp of generating radiation results in the narrowing of the spectrum of terahertz radiation and its redshift. The simulation of the generation of terahertz radiation within the model of three-wave mixing has shown that this effect is due to a change in the phase matching width of the degenerate generation of the difference frequency of terahertz range. In addition, the comparative analysis of terahertz radiation spectra generated in DAST, DSTMS, OH1, and BNA organic crystals indicates that the spectral–temporal properties of terahertz radiation can be more roughly controlled by choosing an appropriate crystal. The proposed approach to control the terahertz radiation spectrum by chirping the pump pulse provides the foundation for spectroscopic studies using intense terahertz radiation with controlled spectral–temporal properties.

The method of the optimal movement trajectory construction in the terrain patrolling tasks is proposed. The method is based on the search of the Hamiltonian circuit on the graph of the terrain map and allows automatic construction of the optimal closed path for arbitrary terrain map. The distinguishing feature of the method is the use of the modified algorithm for the Hamiltonian circuit search. The algorithm can be scaled for the maps corresponding to the graphs with a large (more than 100) number of the vertices, for which the standard brute-force algorithm of the Hamiltonian circuit search requires significantly higher execution time than the proposed algorithm. It is demonstrated that the utilized algorithm possesses 17 times less constant of the time complexity growth than the standard brute-force algorithm. It allows more than one order of magnitude (from 30 to 500 vertices, i.e., approximately to the 17 times) increase of the graph vertices that is used for the Hamiltonian circuit search in the real time (0.1–100 s) regime.

High (15–25) harmonic generation in the vacuum ultraviolet spectral range (83–50 nm) has been realized by focused (NA = 0.033) near-infrared femtosecond laser radiation (wavelength λ = 1.24 μm) with a vacuum intensity of ~7.5 × 10 14 W/cm 2 irradiating a dense gas jet. It has been shown experimentally that the use of such a high-numerical aperture focusing requires high (up to 10 bar) gas jet pressures to optimize phase matching. The use of the dense gas jet results in a noticeable manifestation of nonlinear propagation effects for generating radiation, which affect the generation process through the change in the phase matching conditions. Furthermore, it has been shown that the prechirping of the generating pulse makes it possible to compensate a chirp appearing due to self-phase modulation and to increase the harmonic generation efficiency because of the nonlinear compression of the generating pulse. This approach has allowed 17th (73 nm) harmonic generation with an energy of 2 pJ in a pulse and a generation efficiency of 5.4 × 10 –9 . The estimates obtained have shown that this radiation can be used for single-pulse maskless photolithography in the extreme ultraviolet range.

The implementation of advanced precision farming systems, which are becoming relevant due to rapid technological development, requires the invention of new approaches to the diagnostics and control of the growing process of cultivated crops. This is especially relevant for potato, as it is one of the most demanded crops in the world. In the present work, an analytic model of the dependence of potato tubers mass on carbon dioxide concentration under cultivation in a closed vegetation system is presented. The model is based on the quantitative description of starch molecule synthesis from carbon dioxide under photosynthesis. In the frame of this work, a comprehensive description of the proposed model is presented, and the verification of this model was conducted on the basis of experimental data from a closed urban vertical farm with automated climate control. The described model can serve as a basis for the non-contact non-invasive real-time measurement of potato tuber mass under growth in closed vegetation systems, such as vertical farms and greenhouses, as well as orbital and space crop production systems.

The generation of low-order harmonics in the gas medium by femtosecond laser radiation of unique mid-IR Fe: ZnSe laser system operating at $4.5\ \mu\mathrm{m}$ wavelength is investigated. The dependence of the harmonics generation efficiency on the experimental parameters is studied, that allows optimization of the harmonics yield. The present work is a new step towards high-order harmonics generation driven by low-frequency laser fields.

Low-order (fifth, seventh, and ninth) harmonics have been generated under the interaction of intense (I ~ 1014 W/cm2) femtosecond mid-infrared radiation of a laser system based on a Fe:ZnSe crystal (wavelength is 4.55 μm, pulse duration by the FWHM level of intensity is 160 fs, and the pulse energy is up to 3.5 mJ) with an argon jet (pressure is up to 10 bar) in the tunneling ionization regime (Keldysh parameter is $$\gamma = 0.2$$ ). The maximum energy efficiencies of the 5th, 7th, and 9th harmonic generation are 2 × 10–7, 6 × 10‒9, and 3 × 10–10, respectively. It has been established that nonlinear effects of propagation of generating radiation under an increase in the pressure of the gas jet begin to significantly affect the process of generation.

В данной работе экспериментально исследовано влияние длины и давления газовой струи аргона на процесс генерации гармоник низкого порядка (5, 7, 9, 11) фемтосекундным излучением лазерной системы на кристалле Fe:ZnSe c длиной волны 4.5 мкм. Экспериментально установлено, что увеличение длины среды генерации вплоть до длины перетяжки позволяет более чем на порядок (в 12 раз) увеличить эффективность генерации. Кроме того, показано, что изменение длины газовой среды также приводит к изменению зависимости энергии генерируемого излучения от давления, что является следствием изменения условий фазового согласования, для корректного моделирования которых необходимо учитывать нелинейно-оптические эффекты распространения генерирующего излучения.

We present the single-shot optoacoustic method of the TEMoo mode laser pulse parameters retrieval (pulse duration and beam radius). The experimental proof of the concept is demonstrated with the use of Er:YAG mid-IR nanosecond laser radiation. The proposed method can be applied for any laser wavelength provided that the appropriate highly-absorptive medium was chosen. The presented method can be a subject of interest in the area of laser metrology and applications.

Low-order (fifth, seventh, and ninth) harmonics have been generated under the interaction of intense ( I 10 14 W/cm 2 ) femtosecond mid-infrared radiation of a laser system based on a Fe:ZnSe crystal (wavelength is 4.55 μm, pulse duration by the FWHM level of intensity is 160 fs, and the pulse energy is up to 3.5 mJ) with an argon jet (pressure is up to 10 bar) in the tunneling ionization regime (Keldysh parameter is γ = 0.2 ). The maximum energy efficiencies of the 5 th , 7 th , and 9 th harmonic generation are 2 × 10 –7 , 6 × 10 ‒9 , and 3 × 10 –10 , respectively. It has been established that nonlinear effects of propagation of generating radiation under an increase in the pressure of the gas jet begin to significantly affect the process of generation.

We report on a hybrid optoacoustic method aimed to retrieve the three-dimensional spatial distributions of the plasma electron density and the deposited energy density in the region of plasma formation under optical breakdown in condensed medium. The spatial distribution of the plasma electron density obtained by the proposed method with the accuracy of 3×1018 cm−3 gives the qualitative characterization of the laser pulse propagation in the region of plasma formation. The spatial distribution of the deposited energy density retrieved by the proposed method with the accuracy of 14 J/cm3 provides the quantitative description of the laser impact on the bulk of the medium. The method is based on photoacoustic imaging and shadowgraphy techniques, which have the spatial resolution of 2 μm and 10 μm, respectively. The proposed method can be applied both in the area of technological applications, such as micromachining of transparent materials, and in the field of the fundamental science of laser–matter interaction.

The ranges of energies of femtosecond laser pulses and distances from the focusing point of intense (up to 1013 W/cm2) femtosecond laser radiation to a silicon sample in which phase transitions can be initiated have been determined using the time-resolved shadow photography technique. It has been found that the tight focusing (NA = 0.5) of femtosecond near infrared laser radiation provides a pressure of 15 GPa, which corresponds to a pressure of (40 ± 6) GPa in the case of laser shock peening of silicon and exceeds the threshold value necessary for the initiation of a family of phase transitions (11, 14, and 33 GPa). The pressure on the front of the shock wave propagating in the medium decreases rapidly (in 2.5 ns) below this threshold value, which significantly restricts the possible application regimes of laser shock peening.

We report a study of the photoacoustic energy conversion efficiency under femtosecond filamentation in water. We characterized the interaction of ultra-short laser pulse with water under different temperatures and filamentation regimes.

We present a novel approach to the characterization of ultrafast laser-matter interaction processes in solids and liquids under extreme conditions of microplasma generation. Through the combination of three-dimensional propagation imaging, absorption measurements, shadowgraphy and photoacoustic imaging we can restore plasma electron density distribution, laser pulse fluence profile and the value of deposited energy density inside the bulk of the material and characterize the regime of the laser pulse propagation. The developped concept is important for understanding the physics of ultrafast laser-matter interactions with strong implications for precision control of laser micromachining, bioprocessing and biotreatment.