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L. P. Yatsenko

Publications and source records attributed to L. P. Yatsenko.

17 recordsLinked to original sources
arXiv2020

Evolution of the velocity distribution of atoms under the action of the bichromatic force

We study numerically the evolution of the velocity distribution of atoms under the action of the bichromatic force. The comparison of the time dependencies of the distribution width and the average acceleration of atoms reveal the correlation of these quantities. We show that the estimation of the momentum diffusion coefficient on the basis of the analogy between the interaction of atoms with the counter-propagating bichromatic waves and the interaction of atoms with the counter-propagating sequences of the $π$-pulses roughly corresponds to the results of numerical calculations. To separate the influence of the momentum diffusion on the evolution of atomic momentum distribution from the influence of the time-dependent Doppler shift, we study the motion of a ``heavy'' atom, for which the velocity change during the interaction of an atom with the field can be neglected. Provided that the parameters of the atom-field interaction are optimal, we show that the momentum diffusion coefficient is proportional to the intensity of the laser radiation. We used the Monte Carlo wave-function method for the numerical simulation of the atomic motion.

physics.optics↗
arXiv2016

Ranging with frequency-shifted feedback lasers: from $μ$m-range accuracy to MHz-range measurement rate

We report results on ranging based on frequency shifted feedback (FSF) lasers with two different implementations: (1) An Ytterbium-fiber system for measurements in an industrial environment with accuracy of the order of 1 $μ$m, achievable over a distance of the order of meters with potential to reach an accuracy of better than 100 nm; (2) A semiconductor laser system for a high rate of measurements with an accuracy of 2 mm @ 1 MHz or 75 $μ$m @ 1 kHz and a limit of the accuracy of $\geq $ 10 $μ$m. In both implementations, the distances information is derived from a frequency measurement. The method is therefore insensitive to detrimental influence of ambient light. For the Ytterbium-fiber system a key feature is the injection of a single frequency laser, phase modulated at variable frequency $Ω$, into the FSF-laser cavity. The frequency $Ω_{max}$ at which the detector signal is maximal yields the distance. The semiconductor FSF laser system operates without external injection seeding. In this case the key feature is frequency counting that allows convenient choice of either accuracy or speed of measurements simply by changing the duration of the interval during which the frequency is measured by counting.

physics.ins-det↗
arXiv2014

Cooling and trapping of atoms and molecules by the counter-propagating pulses trains

We discuss a possible one-dimensional trapping and cooling of atoms and molecules due to their non-resonant interaction with the counter-propagating light pulses trains. The counter-propagating pulses form a one-dimensional trap for atoms and molecules, and properly chosen the carrier frequency detuning from the transition frequency of the atoms or molecules keeps the "temperature" of the atomic or molecular ensemble close to the Doppler cooling limit. The calculation by the Monte-Carlo wave function method is carried out for the two-level and three-level schemes of the atom's and the molecule's interaction with the field, correspondingly. The discussed models are applicable to atoms and molecules with almost diagonal Frank-Condon factor arrays. Illustrative calculations where carried out for ensemble averaged characteristics for sodium atoms and SrF molecules in the trap. Perspective for the nanoparticle light pulses's trap formed by counter-propagating light pulses trains is also discussed.

physics.atom-ph↗
arXiv2013

Momentum diffusion of atoms and nanoparticles in an optical trap formed by sequences of counter-propagating light pulses

The motion of atoms and nanoparticles in a trap formed by sequences of counter-propagating light pulses has been analyzed. The atomic state is described by a wave function constructed with the use of the Monte Carlo method, whereas the atomic motion is considered in the framework of classical mechanics. The effects of the momentum diffusion associated with the spontaneous radiation emission by excited atoms and the pulsed character of the atom-to-field interaction on the motion of a trapped atom or nanoparticle are estimated. The motion of a trapped atom is shown to be slowed down for properly chosen parameters of the atom-to-field interaction, so that the atom oscillates around the antinodes of a non-stationary standing wave formed by counter-propagating light pulses at the point where they "collide".

physics.atom-ph↗
arXiv2012

Direct two-photon excitation of isomeric transition in thorium-229 nucleus

A possibility of the two-photon excitation of an isomeric state in a nucleus of thorium-229 has been discussed. The fluorescence intensity of the excitation is demonstrated to be identical for the irradiation of nuclei with either monochromatic light or polychromatic radiation consisting of a sequence of short light pulses of the same intensity. The two-photon excitation of Th^{3+} ion in an electromagnetic trap with a focused laser beam with a wavelength of about 320 nm and power of 100 mW can lead to the absorption saturation, at which the fluorescence emission with the frequency of the transition in a nucleus is maximal. In crystals doped with Th^{4+} to a concentration of about 10^{18} cm^{-3} and irradiated with a laser radiation 10 W in power, the emission of several photons per second with a wavelength of about 160 nm becomes possible.

physics.atom-ph↗
arXiv2012

Performance of a 229 Thorium solid-state nuclear clock

The 7.8 eV nuclear isomer transition in 229 Thorium has been suggested as an etalon transition in a new type of optical frequency standard. Here we discuss the construction of a "solid-state nuclear clock" from Thorium nuclei implanted into single crystals transparent in the vacuum ultraviolet range. We investigate crystal-induced line shifts and broadening effects for the specific system of Calcium fluoride. At liquid Nitrogen temperatures, the clock performance will be limited by decoherence due to magnetic coupling of the Thorium nucleus to neighboring nuclear moments, ruling out the commonly used Rabi or Ramsey interrogation schemes. We propose a clock stabilization based on counting of flourescence photons and present optimized operation parameters. Taking advantage of the high number of quantum oscillators under continuous interrogation, a fractional instability level of 10^{-19} might be reached within the solid-state approach.

physics.atom-ph↗
arXiv2011

Analog of the coherent population trapping state in a polychromatic field

The interaction between a three-level atom and a polychromatic field with an equidistant spectrum (Λ-scheme of the atom--field interaction) has been studied theoretically. It is shown that the interaction of an atom with such a field can be reduced to its interaction with a bichromatic field with additional light shifts of transition frequencies and an additional coupling of the lower atomic levels, which is proportional to the field intensity. Owing to this coupling, the idea of the coherent population trapping can be considered only as an approximation, because the dark state is not an eigenstate of the effective Hamiltonian in the general case of arbitrary dipole moments. The analyzed model gives a simple theoretical interpretation for the formation of the atomic state, which is close to the coherent population trapping, in the radiation field of a femtosecond laser.

physics.atom-ph↗
arXiv2011

Influence of the atomic-wall collision elasticity on the coherent population trapping resonance shape

We studied theoretically a coherent population trapping resonance formation in cylindrical cell without buffer gas irradiated by a narrow laser beam. We take into account non-zero probabilities of elastic ("specular") and inelastic ("sticking") collision between the atom and the cell wall. We have developed a theoretical model based on averaging over the random Ramsey pulse sequences of times that atom spent in and out of the beam. It is shown that the shape of coherent population trapping resonance line depends on the probability of elastic collision.

quant-ph↗
arXiv2011

Dark resonances in the field of frequency shifted feedback laser radiation

We present a theory of dark resonances in a fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency shifted feedback (FSF) laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulses train. We study analytically the field broadening and the light shift of the resonances.

quant-ph↗
arXiv2010

Influence of diffusion of atoms on the dark resonance lineshape in spatially bounded laser fields

We propose a diffusion model for the recently discovered diffusion-induced Ramsey narrowing arising when atoms diffuse in a buffer-gas cell in the laser radiation field. The diffusion equation for the coherence of metastable states coupled with an excited state by laser radiation of different frequencies in a three-level scheme of the atom-field interaction is obtained in the strong-collision approximation. The dependence of the shape of an absorption line near the transmission maximum of one of the frequencies on the two-photon resonance detuning for various geometries of the cell is investigated.

physics.atom-ph↗
arXiv2009

Frequency-modulation saturation spectroscopy of molecular iodine hyperfine structure near 640 nm with a diode laser source

In a frequency-modulation spectroscopy experiment, using the radiation from a single frequency diode laser, the spectra of molecular iodine hyperfine structure near 640 nm were recorded on the transition $B^3Π_{0_u^{+}}-X^1Σ^+_{g}$. The frequency reference given by the value of the modulation frequency (12.5 MHz in given experiment) allows determination of the frequency differences between hyperfine components with accuracy better than 0.1 MHz using the fitting procedure in experiment with only one laser.

physics.atom-ph↗
arXiv2006

Preparation of nondegenerate coherent superpositions in a three-state ladder system assisted by Stark Shifts

We propose a technique to prepare coherent superpositions of two nondegenerate quantum states in a three-state ladder system, driven by two simultaneous fields near resonance with an intermediate state. The technique, of potential application to enhancement of nonlinear processes, uses adiabatic passage assisted by dynamic Stark shifts induced by a third laser field. The method offers significant advantages over alternative techniques: (ı) it does not require laser pulses of specific shape and duration and (\ii) it requires less intense fields than schemes based on two-photon excitation with non-resonant intermediate states. We discuss possible experimental implementation for enhancement of frequency conversion in mercury atoms.

quant-ph↗
arXiv2003

Pulse-driven near-resonant quantum adiabatic dynamics: lifting of quasi-degeneracy

We study the quantum dynamics of a two-level system driven by a pulse that starts near-resonant for small amplitudes, yielding nonadiabatic evolution, and induces an adiabatic evolution for larger amplitudes. This problem is analyzed in terms of lifting of degeneracy for rising amplitudes. It is solved exactly for the case of linear and exponential rising. Approximate solutions are given in the case of power law rising. This allows us to determine approximative formulas for the lineshape of resonant excitation by various forms of pulses such as truncated trig-pulses. We also analyze and explain the various superpositions of states that can be obtained by the Half Stark Chirped Rapid Adiabatic Passage (Half-SCRAP) process.

quant-ph↗
arXiv2002

Adiabatic creation of entangled states by a bichromatic field designed from the topology of the dressed eigenenergies

Preparation of entangled pairs of coupled two-state systems driven by a bichromatic external field is studied. We use a system of two coupled spin-1/2 that can be translated into a three-state ladder model whose intermediate state represents the entangled state. We show that this entangled state can be prepared in a robust way with appropriate fields. Their frequencies and envelopes are derived from the topological properties of the model.

quant-ph↗
arXiv2001

On the topology of adiabatic passage

We examine the topology of eigenenergy surfaces characterizing the population transfer processes based on adiabatic passage. We show that this topology is the essential feature for the analysis of the population transfers and the prediction of its final result. We reinterpret diverse known processes, such as stimulated Raman adiabatic passage (STIRAP), frequency-chirped adiabatic passage and Stark-chirped rapid adiabatic passage (SCRAP). Moreover, using this picture, we display new related possibilities of transfer. In particular, we show that we can selectively control the level which will be populated in STIRAP process in Lambda or V systems by the choice of the peak amplitudes or the pulse sequence.

quant-ph↗
arXiv1999

Photoionization Suppression by Continuum Coherence: Experiment and Theory

We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS) in the photoionization continuum of helium out of the metastable state 2s $^1S_0$. The continuum dressing with a 1064 nm laser, couples the same region of the continuum to the {4s $^1S_0$} state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by as much as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a contiuum. We present experimental results demonstrating the effect of pulse delay upon the LICS, and for the behavior of LICS for both weak and strong probe pulses. Simulations based upon numerical solution of the Schrödinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wavefunctions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS. We show that in the case of a probe pulse shorter than the dressing one the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS. We discuss some consequences of deviation from steady-state theory.

physics.atom-ph↗