arXiv subjects

V. L. Velichansky

Publications and source records attributed to V. L. Velichansky.

16 recordsLinked to original sources

arXiv2025

Dual-frequency Doppler-free crossover resonance with suppressed magnetic-field sensitivity for compact optical frequency standards

We report the observation and characterization of a high-contrast dual-frequency Doppler-free ground-state crossover resonance in the D1 line of 87Rb.The crossover appears at a two-photon detuning exceeding the natural linewidth of the excited state and is formed by the optical pumping effect. Unlike the previously proposed resonance at zero two-photon detuning, which we show becomes sensitive to magnetic-field fluctuations due to residual ellipticity of the optical fields-resulting in frequency shifts and profile asymmetry-the crossover resonance is largely immune to this effect. Our theoretical analysis attributes the observed sensitivity to the dispersive contribution of ground-state coherences to absorption. Stability measurements under magnetic-field fluctuations demonstrate that using the crossover resonance provides more than an order-of-magnitude improvement, making it a promising reference for frequency stabilization in compact, field-deployable optical standards.

physics.atom-ph↗

arXiv2025

Nuclear-spin-related properties of~the dual-frequency Doppler-free resonance

We investigate the dual-frequency Doppler-free resonance in the D1 line of alkali-metal atoms for any accessible value of the nuclear spin I. The consideration is performed using the symmetries of the dipole operator and the basis, where the quantization axis is directed along the polarization of the one of optical waves. We show that there is the absence of the optical pumping in the scheme with parallel polarizations for the center of the crossover, resulting in its smallest width. Secondly, the growth in the absorption for the center of the peak with Fe=I-1/2 and the decrease of its width with the two-photon detuning in the case of~orthogonal polarizations is explained. Particular attention is paid to the special case of I=3/2, where this effect is the most pronounced. The experiment with 87Rb, 85Rb, and 133Cs atoms is in agreement with the analysis.

physics.atom-ph↗

arXiv2025

Single-frequency inverted Doppler-free resonance as a platform for chip-scale optical clock

We report on the possibility to obtain a high-quality inverted Doppler-free resonance in D1 line of alkali-metal atoms in the single-frequency regime. The counter-propagating optical fields with linear and mutually orthogonal polarizations and the transition Fg=I+1/2 --> Fe=I-1/2 are proposed to the use. We establish the best possible nuclear spin value and the corresponding atomic isotope for this regime. Our experiment demonstrates that the resonance contrast-to-width ratio in the single-frequency regime is practically the same as in the dual-frequency regime, which simplifies the optical module to be used in compact optical clocks. The achieved short-term frequency stability is 3*10^(-13) at 1 s, which is comparable to results that can be obtained with the dual-frequency technique.

physics.atom-ph↗

arXiv2024

Frequency locking: a distinctive feature of the coherent population trapping and the stationarity effect

We study the case where phase modulation of the harmonic signal is used to obtain the error signal for the frequency stabilization to a reference atomic transition. High-frequency modulation, or analog of the Pound-Drever-Hall regime, is considered. We demonstrate that for coherent population trapping, the maximal error-signal slope retains at a certain level with growth in the modulation frequency, while for other types of resonances it drops steadily. The investigation of the low-frequency modulation regime reveals the stationarity effect. We show that in this case, the maximal steepness of the error signal does not depend on the modulation frequency and is reached at a fixed value of the frequency deviation.

quant-ph↗

arXiv2023

A nonlinear frequency shift caused by asymmetry of the coherent population trapping resonance: a generalization

We investigate the coherent population trapping resonance induced by a polychromatic optical field with an asymmetric spectrum, i.e., whose sidebands equidistant from the carrier have unequal powers. A situation is considered where a modulation is used to provide the so-called in-phase and quadrature signals in the optical field's transmission, which are used for stabilization of the local oscillator's frequency in chip-scale atomic clocks. In a general case, the frequencies of the signals nonlinearly depend on the optical field's intensity due to the asymmetry of the resonance. In this work, we demonstrate a) that this effect stems from a multi-peak structure of the resonance; b) a linear dependence of the frequency on the optical field's intensity at high modulation values; c) that the regime of the resolved structure has more advantages than suppression of the frequency shift due to the spectrum asymmetry.

physics.optics↗

arXiv2023

Effect of depolarizing and quenching collisions on contrast of the coherent population trapping resonance

We investigate the effect of buffer gases on the coherent population trapping resonance induced by a $σ$-polarized optical field in $^{87}$Rb atoms. Our experimental results show that inert gases, which depolarize the excited state of the alkali-metal atoms, provide higher contrast than nitrogen that effectively quenches their fluorescence. We also demonstrate that elimination of the spontaneous radiation does not significantly decrease the width at moderate temperatures of an atomic medium. Therefore, a mixture of inert gases can be preferable over a mixture with nitrogen for atomic clocks.

quant-ph↗

arXiv2021

Intensity nonlinearity of the error-signal frequency shift in the modulation spectroscopy of dark resonances and approaches to its reduction

We have found that the error-signal frequency corresponding to the coherent population trapping resonance can be displaced from that of "$0-0$" transition unperturbed by the optical field, although the frequency is not sensitive to changes in its intensity. We consider the double $Λ$-system of levels interacting with the asymmetric polychromatic optical field to demonstrate that this effect arises due to intensity nonlinearity of the error-signal frequency shift. The experiment with $^{87}$Rb atoms in Ar-N$_2$ buffer gas atomic cell shows how the displacement value depends on different parameters. The possible influence of the effect on the clocks' frequency stability and reproducibility are discussed.

quant-ph↗

arXiv2020

Dynamic continuous-wave spectroscopy of coherent population trapping at phase-jump modulation

A method of dynamic continuous-wave spectroscopy of coherent population trapping (CPT) resonances using phase modulation of the jump type is developed. The time evolution of the spectroscopic signal is investigated. A method for the formation of an error signal for frequency stabilization is proposed. We show that our approach has a reduced sensitivity to the lineshape asymmetry of the CPT resonance. The experimental results are in good qualitative agreement with theoretical predictions based on a mathematical model of a three-level $Λ$ system in a bichromatic field. This method can be used in atomic frequency standards (including chip-scale atomic clocks).

physics.atom-ph↗

arXiv2013

Feedback spectroscopy of atomic resonances

We propose a non-standard spectroscopic technique that uses a feedback control of the input probe field parameters to significantly increase the contrast and quality factor of the atomic resonances. In particular, to apply this technique for the dark resonances we sustain the fluorescence intensity at a fixed constant level while taking the spectra process. Our method, unlike the conventional spectroscopy, does not require an optically dense medium. Theoretical analysis has been experimentally confirmed in spectroscopy of atomic rubidium vapor in which a considerable increase (one-two order) of the resonance amplitude and a 3-fold decrease of the width have been observed in optically thin medium. As a result, the quality factor of the dark resonance is increased by two orders of magnitude and its contrast reaches a record level of 260%. Different schemes, including magneto-optical Hanle spectroscopy and Doppler-free spectroscopy have also showed a performance enhancement by using the proposed technique.

physics.atom-ph↗

arXiv2010

EIT-based Vector Magnetometry in Linear Polarized Light

We develop a generalized principle of EIT vector magnetometry based on high-contrast EIT-resonances and the symmetry of atom-light interaction in the linearly polarized bichromatic fields. Operation of such vector magnetometer on the D1 line of 87Rb has been demonstrated. The proposed compass-magnetometer has an increased immunity to shifts produced by quadratic Zeeman and ac-Stark effects, as well as by atom-buffer gas and atom-atom collisions. In our proof-of-principle experiment the detected sensitivity to magnetic field orientation is 10^{-3} deg/Hz^{1/2}, which is limited by laser intensity fluctuations, light polarization quality, and the magnitude of the magnetic field.

physics.atom-ph↗

arXiv2006

Features of Magneto-Optical Resonances in an Elliptically Polarized Traveling Light Wave

The parameters of nonlinear absorption magneto-optical resonances in the Hanle configuration have been studied as functions of the ellipticity of a traveling light wave. It has been found that these parameters (amplitude, width, and amplitude-to-width ratio) depend strongly on the polarization of the light wave. In particular, the resonance amplitude can increase by more than an order of magnitude when the polarization changes from linear to optimal elliptic. It has been shown that this effect is associated with the Doppler frequency shift for atoms in a gas. The theoretical results have been corroborated in experiments in Rb vapor.

quant-ph↗

arXiv2005

Experimental Investigation of the Dark Pseudoresonance on the D1 Line of the 87Rb Atom Excited by a Linearly Polarized Field

The measurements of the metrological characteristics (amplitude, width, and shift in the magnetic field) of the dark pseudoresonance, which was proposed by Kazakov et al. [quant-ph/0506167] as the reference resonance for an atomic frequency standard, are reported. It has been shown that the characteristics of the pseudoresonance are worse than those of the unsplit electromagnetically induced transparency resonance for the excitation scheme with the lin||lin polarization on the D1 line of the 87Rb atom.

physics.atom-ph↗

arXiv2005

Experimental preparation of pure superposition states of atoms via elliptically polarized bichromatic radiation

We propose a simple and effective way of creating pure dark superposition states. The generation of pure states is carried out by using bichromatic radiation with controllable polarization ellipticity. We derived analytic formulas for polarization elipticity to obtain pure dark states of different Zeeman sublevels of alkali atoms. Experimentally we accumulated ~60% of the atoms in the 0-0 dark state of the D1 line of Rb87

physics.atom-ph↗

arXiv2005

On the unique possibility to increase significantly the contrast of dark resonances on D1 line of $^{87}$Rb

We propose and study, theoretically and experimentally, a new scheme of excitation of a coherent population trapping resonance for D1 line of alakli atoms with nuclear spin $I=3/2$ by bichromatic linearly polarized light ({\em lin}$||${\em lin} field) at the conditions of spectral resolution of the excited state. The unique properties of this scheme result in a high contrast of dark resonance for D1 line of $^{87}$Rb.

quant-ph↗

arXiv2005

Pure superposition states of atoms generated by a bichromatic elliptically polarized filed

We find specific polarizations of components of a bichromatic field, which allow one to prepare pure superposition states of atoms, using the coherent population trapping effect. These $m$$-$$m$ states are prepared in the system of Zeeman substates of the ground-state hyperfine levels with arbitrary angular momenta $F_1$ and $F_2$. It is established that, in general case $m\ne 0$, the use of waves with elliptical polarizations ($ε_1$$\perp$$ε_2$ field configuration for alkali metal atoms) is necessary for the pure state preparation. We analytically show an unique advantage of the D1 line of alkali metal atoms, which consists in the possibility to generate pure $m$$-$$m$ states even in the absence of spectral resolution of the excited-state hyperfine levels, contrary to the D2 line.

quant-ph↗

arXiv1999

Enhancement of Magneto-Optic Effects via Large Atomic Coherence

We utilize the generation of large atomic coherence to enhance the resonant nonlinear magneto-optic effect by several orders of magnitude, thereby eliminating power broadening and improving the fundamental signal-to-noise ratio. A proof-of-principle experiment is carried out in a dense vapor of Rb atoms. Detailed numerical calculations are in good agreement with the experimental results. Applications such as optical magnetometry or the search for violations of parity and time reversal symmetry are feasible.

quant-ph↗