Laser Radiation Frequency Research Articles

The effect of laser treatment modes on the colors of the steel 04H18H10

The purpose of the study of this article is to identify the effect of laser treatment modes on the color of the steel 04X18H10.The research methods were reduced to determining ranges for each of the parameters with an example of the desired color. The influence of laser radiation parameters: the power and frequency of laser radiation, the speed of the laser beam, the resolution of the fill of the marked object - contributes to obtaining a certain shade of the color palette according to the RAL standard.The result of the study was the data obtained, according to which it is safe to say that the speed of movement of the laser beam has a direct effect on the resulting semitone color. At high values of this parameter, the colors become closer to dark halftones, whereas a decrease in speed leads to the opposite effect, it is possible that at low speeds of the laser beam, a slower heating of the object occurs, which leads to light halftones, and with a gradual increase in speed and, accordingly, a possible increase in surface heating temperature, colors begin to form a dark tone. The results obtained by changing the fill resolution parameter make it clear that an increase in this indicator directly affects the saturation of the resulting color with its increase, whereas a decrease in the number of fill lines causes a drop in the color saturation of the marked object.Conclusion. In this paper, the influence of the factors responsible for obtaining various shades of colors during laser marking of metal is considered, a basic palette of colors is obtained for its subsequent expansion and use for artistic purposes.

Лабораторная работа «Изучение многофотонной ионизации в условиях резонансного возбуждения атомарных паров»

The developed laboratory work is described, designed to study multiphoton ionization under conditions of resonant excitation of atomic vapors by frequency-tunable laser radiation. Atomic pairs of potassium and rubidium were chosen as objects of study. To demonstrate the resonant nature of multiphoton ionization, the results of studies of the dependence of the magnitude of the ion signal on the frequency of laser radiation causing this signal are presented. Analytical expressions are given to describe the experimentally observed patterns of resonant ionization processes. Laboratory work is part of a set of works on the study of resonant nonlinear optics for students studying physics at universities.

The Role of Axions in the Formation of Frequency and Angular Spectra of Laser Radiation Propagated in a Dispersion Medium

The Role of Axions in the Formation of Frequency and Angular Spectra of Laser Radiation Propagated in a Dispersion Medium

Теоретическое исследование влияния рассеивающей среды, состоящей из атомов калия, на время затухания люминесцентного сигнала с использованием метода Монте-Карло

The study solves the problem of the luminescent photons propagation in a resonantly absorbing medium consisting of atoms of the studied substance and a buffer inert gas. The Monte Carlo method was used in numerical experiments carried out to simulate real processes that occur in a chamber designed to determine the lifetime of an individual atom in an excited state by the method of measuring the luminescence intensity decay time. Findings of the research show that when luminescent photons are repeatedly scattered (scattering means the process of absorption and re-emission of a photon by an atom) in a medium, the luminescence decay time noticeably increases, reaching a value greater than the average lifetime of an individual atom in an excited state. The reflection of photons from the walls that make up the chamber can lead to errors in measuring the lifetime. The process of luminescence decay is studied theoretically for various detunings of the laser frequency from the resonant transition frequency. A three-level model of the atom and a model of complete frequency redistribution were applied. The study describes an algorithm based on the Monte Carlo method, which is used to model the three-level population kinetics, laser radiation transfer, radiation trapping, and frequency redistribution

Quantum Peltier coefficient resonance in a GaAs/GaAsAl parabolic quantum well with confined optical phonons

The resonance of the quantum Peltier coefficient (qPC) in a parabolic quantum well (PQW) of GaAs/GaAsAl, subjected to a dc electric field, a magnetic field and a laser radiation, has been theoretically studied by using the quantum kinetic equation method with the assumption that the confined electron-confined optical phonon scattering is essential. The obtained analytical expression for the qPC in PQW is as a function of external fields, PQW parameters, and especially the quantum number m which was changed in order to characterize the influence of confined optical phonon. When m is set to zero, we obtain the results that corresponds to the case of unconfined optical phonon. Numerical calculations are also achieved for a PQW of GaAs/GaAsAl. The obtained results show that the qPC reaches resonance peaks when investigating its dependence on magnetic field and on frequency of laser radiation. Due to the influence of confined optical phonon, the position of resonance peaks has been not only shifted but also more pronounced than in the case of unconfined optical phonon. Besides, as the amplitude of laser radiation increases, the qPC has additional resonance peaks.

Two-level gas laser with transverse diode pumping

We theoretically study a new method for generating laser radiation by a two-level system without population inversion in the ‘red’ wing of its spectral line under resonant absorption of broadband radiation from pump laser diodes. A two-level system simulates the atoms of an active gas in an atmosphere of a high-pressure buffer gas. The effect results from the fact that in the ‘red’ wing of the spectral line, the probability of stimulated emission exceeds the probability of absorption if the homogeneous broadening due to the interaction of particles with the buffer gas significantly exceeds the natural one (at high pressures of the buffer gas). Analytical formulae are obtained that describe the operation of a two-level gas laser with transverse diode pumping. It is found that the longer the active medium, the higher the buffer gas pressure and pump radiation intensity, and the smaller the width of the pump radiation spectrum, the greater the efficiency of conversion of pump radiation into laser radiation. In a sufficiently long active medium (the length of the medium is 50 times its width), the conversion efficiency can reach 44 % at a buffer gas pressure of 5 atm, a pump diode radiation intensity of 3 kW cm−2, and a half-width of its spectrum of 1 cm−1. A two-level gas laser with transverse diode pumping is capable of generating continuous optical radiation with a very high (up to 100 kW) power. The frequency of laser radiation can be tuned by several tens of cm−1.

Development of the technology of nonlinear optical ZnGeP<sub>2</sub> crystals and laser radiation frequency converters for atmospheric gas analysis systems

Development of the technology of nonlinear optical ZnGeP<sub>2</sub> crystals and laser radiation frequency converters for atmospheric gas analysis systems

The diagnostics to study the spatial-angular distribution of radiation scattered by plasma at the "Kanal-2" facility

A fiber-optics-based diagnostics to study the spatial-angular scattering of radiation by plasma in the spectral range of 400–1900 nm is presented. Introducing light filters into the image registration system enables to choose the entire spectral range or a selected one. The proposed method allows to carry out studies simultaneously in different planes, which gives information about the scattering process isotropy. This method can be used to record on digital camera matrix the energy evenly distributed over the area of the fiber input end face, starting from values of 10−12 J at a wavelength of 0.532 µm, 10−11 J - at 0.632 µm, and 10−7 J - at 1.064 µm. Experiments carried out with the interaction of Nd:glass laser radiation with a solid copper target have shown that the scattering process is not isotropic, and the scatterplots in experiments with the fundamental frequency of laser radiation and its second harmonic differ.

Investigation of the transition at a wavelength of 506 nm, intended for deep cooling of thulium atoms

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 at a wavelength of 506.2 nm is detected in a magneto-optical trap with the employment of the developed laser setup. The value of hyperfine splitting of the transition upper level is measured, and the single-dimension cooling at this wavelength is observed for the first time.

Generation of intense coherent electromagnetic radiation during the interaction of a multi-terawatt laser pulse with a nanowire target* *Reported at the 4th International Conference on Ultrafast Optical Science (Russia, Moscow, FIAN, 28 September – 2 October 2020).

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 shape of the laser pulse. In the first regime, when the laser pulse is long enough (tens and hundreds of femtoseconds), electrons are only partially forced out of the target. The characteristics of the low-frequency part of the spectrum of the generated radiation are determined in this case by the duration of the laser pulse, as well as by its amplitude and target parameters (geometric dimensions and concentration of electrons). In the second regime, the laser pulse has a large amplitude and a steep rising edge (the amplitude of the first half-wave is of the order of the maximum pulse amplitude); as a result, most of the electrons are displaced from the target already at the initial moment of interaction. In this regime, unipolar and bipolar pulses with a duration of tens of laser field periods can be formed. Changing the target length makes it possible to control the period of field oscillations and their number in the generated radiation. In the intermediate regime of short laser pulses with an insufficiently steep rising edge, oscillations of the formed electron bunches can occur in the macroscopic Coulomb attraction field of the charged target, which gives rise to radiation with a frequency several times lower than that of laser radiation. In this case, the pulses of the generated radiation contain a few cycles of the field with decreasing amplitude and increasing frequency. Using numerical simulation in three regimes of interaction, the characteristics of IR and terahertz radiation are found, in particular, the pulse shapes, ranges of generated frequencies, amplitudes and angular distributions of radiation are determined. It is shown that the amplitude of the generated pulse can reach subrelativistic and relativistic values (the field strength is more than 1 TV m−1 at a frequency ten times lower than the laser radiation frequency), and the energy conversion efficiency can be of the order of one percent.

Flicker Noise in Diode Laser Spectroscopy

Low-frequency (flicker) noises of the intensity and frequency of diode laser (DL) radiation have been studied. A model of DL flicker noise and a method for minimizing flicker noise at which the relative photocurrent noise can be registered at a level of 5 × 10–7 with an averaging time of 100 ms are proposed. The results obtained can be used in the development of DL-based gas-analytical equipment for measuring low gas concentrations.

Long ULE Cavities with Relative Fractional Frequency Drift Rate below 5 × 10–16/s for Laser Frequency Stabilization

Two ultrastable laser systems for the clock transition spectroscopy in the strontium frequency standard are developed. The high stability of laser radiation frequency is provided by the active loop for frequency referencing to the Fabry–Perot reference cavity. The used cavities are made of glass with ultra-low thermal expansion coefficient and are 48 cm long which provides an extremely low thermal noise limit of 7 × 10–17. The relative frequency drift velocity of laser systems is 216 mHz/s which allows the implementation of high-accuracy spectroscopy of the clock transition in strontium.

The Ettingshausen effect in doped semiconductor superlattice under the influence of confined optical phonon

The electron – optical phonon scattering is considered in detail to studying the Ettingshausen effect in doped semiconductor superlattice under the influence of phonon confinement and laser radiation. The analytical expressions for tensors and the Ettingshausen coefficient are obtained by using the kinetic equation method. The Ettingshausen coefficient depends on temperature of the sample, amplitude and frequency of laser radiation, magnetic field and the quantum number m specific for the confinement of phonon. The dependences are clearly displayed in the numerical results for GaAs:Be/GaAs:Si doped semiconductor superlattice. The magnetic field makes the Ettingshausen coefficient change in quantitative under the influence of temperature or laser amplitude and change the resonance condition. The numerical results show that both resonance condition and resonance peaks position are affected by the increase of quantum number m. We also get the result corresponding to the unconfined optical phonon case when m is set to zero. Due to the change of the wave function and energy spectrum of electrons, most of results for the Ettingshausen effect in doped semiconductor superlattice obtained are different from the case of bulk semiconductor. Moreover, in comparison with the case of unconfined optical phonon, under the influence of phonon confinement effect, the Ettingshausen coefficient changes in magnitude, the number and position of resonance peaks.

Compensation of residual amplitude modulation fluctuations in an optoelectronic system for laser radiation frequency stabilisation

Fluctuations of residual amplitude modulation in a scheme of laser frequency stabilisation by a Fabry – Perot cavity reduce the frequency stability of the laser systems intended for interrogating clock transitions of atoms and ions. The dependences of the residual amplitude modulation on a temperature of the waveguide-based electro-optical modulator used for modulating the radiation phase and on polarisation of the radiation are measured. The parameters are found, at which the influence of the residual amplitude modulation on the frequency stability is minimal. A system for active compensation is created, which reduces the contribution of fluctuations of residual amplitude modulation to the instability down to 2.1 × 10−16, which makes it possible to reach the thermal noise limit of a silicon cryogenic cavity.

The quantum Ettingshausen effect in parabolic quantum wells with in-plane magnetic field in the presence of laser radiation under the influence of confined optical phonon

The quantum Etttingshausen e˙ect in a parabolic quantum well subjected to a constant electric field, magnetic field in the presence of laser radiation is studied by using the quantum kinetic equation method. The analytic expressions for conductivity tensors and dynamic tensors as well as the Ettingshausen coe˚cient (EC) are obtained in the case of the confined electron-confined optical phonon (COP) scattering. The EC depends on specific quantities for external field (such as magnetic field, amplitude and frequency of laser radiation), temperature of the system and quantum well length, especially quantum number m-characterizing the confinement of optical phonon (OP). When m is set to zero, we get the results corresponding to the case of unconfined OP. The analytic results are numerically evaluated and graphed for GaAs/AlGaAs parabolic quantum well. When examining the e˙ect of temperature, the EC has greater values due to the COP. Meanwhile, when quantum well length and amplitude of the laser radiation (LR) increase, the EC has greater values without the confinement of OP. Because of the approach of system to bulk semiconductor structure when the quantum well length approaches micrometer-size, the EC reaches constant. The quantum number m leads to the change of resonance peaks position within the change of the magnetic field and the frequency of LR. In addition, the EC exerts non-linear dependence on the amplitude the LR. All results indicated that the COP a˙ects not only qualitatively but also the transformation rules of the EC. It provides new insights and contributes to the orientation of research into quantum e˙ects in low-dimensional semiconductor systems (LDS).

Nonlinear Photoacoustic Response on Mechanical Stresses in the Vicinity of a Hole in a D16 Aluminum-Alloy Plate

Characteristics of a photoacoustic signal depending on mechanical stresses in the vicinity of a hole in a D16 aluminum-alloy plate have been analyzed. A new nonlinear photoacoustic effect was found that consists in the occurrence of a nonlinear component in the photoacoustic signal depending on mechanical stresses in the vicinity of a hole. This dependence is detected in the signal on the main modulation frequency of laser radiation. We have proposed a theoretical description of the detected effect of thermoelastic generation of ultrasound in stressed metals based on taking into account the thermal impact of laser radiation on their electron subsystem.

Fluorescence of rubidium vapor in a transient interaction regime

We have studied modification of the fluorescence spectra of a room-temperature atomic rubidium vapor in the region of 85 R b and 87 R b D 2 lines while changing the temporal rate of linear (triangular) scanning of laser radiation frequency. An increase in the ramping speed over a certain value ( ≈ 10 6 M H z / s ) results in essential modification of magnitudes of individual atomic transitions, different on rising and falling slopes, which characterize transition from a steady-state interaction regime to a transient one. Our experimental results are very consistent with the developed theoretical model. The obtained results can be used for determination of atomic system parameters such as ground-state relaxation rate. Possible follow-up actions for the addressed control of atomic level population are discussed.

Studies on Charge Carrier Transport in an Injection Laser with Frequency Modulation of the Optical Radiation

One of the promising approaches to solve the problem of increasing the efficiency for interelement connections consists in the use of integrated optical switching systems, whose main elements represent injection lasers with functionally integrated optical radiation modulators. Injection lasers make it possible to modulate the laser radiation by subpicosecond controlling pulses at a constant pumping current, as well as making it possible to implement the sources and modulators of optical radiation in a united AIIIBV nanoheterostructure with second-type heterojunctions. This work is devoted to the studies concerning the transport of charge carriers within a functionally integrated modulator laser with internal frequency modulation of the generated optical radiation using a proposed two-dimensional diffusion-drift model and a numerical simulation technique. The results of the numerical simulation of charge carrier transport in a modulator laser when the pumping current is switched on, as well as under pulsed variation of the controlling voltage, take the structural features, the transport effects, the mechanisms of stimulated and spontaneous radiative recombination, and the photon lifetime into account. It is shown that the maximum modulation frequency of laser radiation is determined by the subpicosecond time of the controlled spatial relocation of the charge-carrier density maxima in the quantum zones of the modulator laser, as well as by the photon lifetime in the laser resonator, and corresponds to the terahertz range. To increase the maximum modulation frequency, it is necessary to reduce the photon lifetime in the active zone of the modulator laser to values lower than 3 ps by changing the resonator’s parameters in a corresponding manner. The proposed model and the method of numerical simulation make it possible to optimize the parameters of a functionally integrated modulator laser, and to provide the required relationships between the maximum modulation frequency of the optical radiation, the modulation coefficient, and the density of the threshold pumping current.

Role of Spectral Line Profile in Laser IR Analysis of Multicomponent Gas Mixtures

Topical issues of the quantitative analysis of multicomponent gas mixtures with use of laser absorption infrared technologies are addressed. It is shown that a number of questions exist regarding the detection of pollutants using these technologies, and these concern not only the position of the center of the analytical line of the detected substance but also the shape of its profile, especially in case of strong intermolecular interactions under conditions of open atmosphere. A number of examples show various aspects of the influence of the error of the spectroscopic model embedded in the solution of the inverse problem (the width and shape of the laser spectral line and gas absorption lines) on the determination of gas concentrations. The parameters of the sensitivity and selectivity of laser gas analysis that support making the optimal choice of laser radiation frequencies for studying specific gas mixtures are discussed. The importance of the high monochromaticity of laser lines, the smooth tuning of the radiation frequency over a wide spectral range, and the adequate simulation of the IR spectra of multicomponent gas mixtures are demonstrated.

Infrared laser-induced isotope-selective dissociation of mixed (CF3Br)mArn van der Waals clusters

The paper presents the results of studies of IR laser-induced bromine-isotope-selective dissociation of small mixed (CF3Br)mArn van der Waals clusters (m = 1, 2 and 1 ≤ n ≤ 5 is the number of molecules and atoms in the clusters, respectively). The experiments used a pulsed CO2 laser to excite clusters and a quadrupole mass spectrometer to detect a molecular cluster beam. The research method is based on the selective vibrational excitation of clusters by IR laser radiation, leading to their predissociation. The possibilities of implementing bromine-isotope-selective dissociation of clusters are considered. The experimental setup and research method are briefly described. The results of determining the cluster dissociation efficiency and selectivity as functions of the energy and frequency of laser radiation are presented. It is shown that resonant vibrational excitation of clusters makes it possible to induce their isotope-selective dissociation. Thus, using a CF3Br/Ar mixture with a pressure ratio of 1/200, the enrichment factors of the 79Br isotope are found to be Kenr(79Br) = 1.15 ± 0.04 and 0.95 ± 0.03 under cluster irradiation conditions on the 9R(30) (ν = 1084.635 cm−1) and 9R(24) (ν = 1081.087 cm−1) lines, respectively The achieved dissociation selectivities for the clusters are, respectively, 1.16 ± 0.05 and 0.95 ± 0.04. The results obtained suggest that this method can be used to separate isotopes in molecules containing isotopes of heavy elements, which have a slight isotopic shift in the IR absorption spectra.