arXiv subjects

D. V. Brazhnikov

Publications and source records attributed to D. V. Brazhnikov.

11 recordsLinked to original sources

arXiv2025

Atomic magnetometry based on the ground-state Hanle effect in an elliptically polarized light wave

We investigate the ground-state Hanle effect in alkali-metal vapor irradiating by a resonant elliptically polarized light wave. The magneto-optical resonances are observed as a change in the ellipticity parameter of the light wave polarization when scanning the transverse magnetic field near zero. We use a miniature ($\approx\,$$0.125$ cm$^3$) glass cesium vapor cell heated to a relatively low temperature of $\approx\,$$85^\circ$C. Under the current experimental conditions, the sensitivity of magnetic field measurements is limited by a technical noise, reaching $180$ fT/$\surd$Hz in a $200$ Hz bandwidth. The ultimate photon-shot-noise-limited sensitivity of the method is estimated to be $\approx\,$$5$ fT/$\surd$Hz. The proposed scheme is promising for the development of a zero-field atomic magnetometer with reduced heat dissipation of the sensor head and relaxed requirements for magnetic shielding compared to counterparts operating in the spin-exchange relaxation-free regime. These features are of particular value for biomedical applications.

physics.atom-ph↗

arXiv2025

Reduction of Magnetic-Field-Induced Shift in Quantum Frequency Standards Based on Coherent Population Trapping

We investigate the magnetic-field-induced frequency shift (MFS) of the clock "0-0" transition in the microwave quantum frequency standard (atomic clock) based on coherent population trapping (CPT) in $^{87}$Rb vapor. To scan the CPT resonance and to form the error signal, a method analogous to the Pound-Drever-Hall (PDH) technique in the optical frequency range is employed, where the modulating frequency ($f_m$) significantly exceeds the resonance linewidth (FWHM). The experiments demonstrate that this technique offers brilliant capabilities for controlling the sensitivity of the clock transition frequency to magnetic field variations in the vapor cell compared to the conventional method with low-frequency modulation ($f_m$$\,\ll\,$FWHM). Specifically, the PDH technique provides several optimal values of the bias magnetic field generated by the solenoid, at which the "0-0" transition frequency exhibits extremely low sensitivity to small variations in the external magnetic field. Furthermore, these magnetic field values can be easily adjusted by changing $f_m$, which is relevant for optimization of the atomic clock's operating regime. The experimental results show that by using the PDH technique, the influence of MFS on the clock transition can be suppressed down to $\approx\,$$3.2$$\,\times\,$$10^{-13}$$δB^2$ mG$^{-2}$. These findings can be leveraged both to relax stringent requirements for magnetic field shielding in state-of-the-art CPT-based miniature atomic clocks (MACs) and to build a new generation of such clocks with long-term frequency stability better than $10^{-12}$.

physics.atom-ph↗

arXiv2024

Method of measuring the chromatic dispersion parameter of optical fibers using a single-arm interferometer and a fiber femtosecond frequency comb

We propose and study a method for measuring the chromatic dispersion parameter (D) of optical fibers and bulk optical elements through the use of a single-arm three-wave interferometer and a fiber femtosecond frequency comb (FFFC). The FFFC is frequency locked to a single-ytterbium-ion optical standard and employed as a source of highly stable and broadband laser radiation. The FFFC spectrum ranges from 1 to 2 microns, which is the most demanded range in fiber optics. The theoretical model presented in the work is used to derive analytical expressions for the parameter D, taking into account the second-order group velocity dispersion. To validate the methodology, the parameter D is measured for a standard single-mode SMF-28 fiber. The proposed method enables the precise measurement of the parameter D with high accuracy across a broad spectral range in a relatively short time.

physics.optics↗

arXiv2023

Light Shift Suppression in Coherent-Population-Trapping Atomic Clocks in the Field of Two Circularly Polarized Light Beams

The state-of-the-art miniature atomic clocks (MACs) are based on the phenomenon of coherent population trapping (CPT) in alkali-metal atomic vapors (Rb or Cs). Increasing frequency stability of the clocks is an urgent issue that will lead to significant progress in many fields of application. Here, we examine a light field configuration composed of two bichromatic light beams with opposite handedness of their circular polarization. The beams are in resonance with optical transitions in the Cs D$_1$ line ($λ$$\approx$$895$ nm). This configuration has already been known for observing CPT resonances of an increased contrast compared to a standard single-beam scheme. However, in contrast to previous studies, we use a scheme with two independent pump and probe beams, where the probe beam transmission is separately monitored. The experiments are carried out with a buffer-gas-filled $5$$\times$$5$$\times$$5$ mm$^3$ vapor cell. It is shown that the resonance's line shape acquires asymmetry which can be efficiently controlled by a microwave (Raman) phase between the beams. As a proof of concept, we study the way how this asymmetry can help to significantly mitigate the influence of ac Stark (light) shift on a long-term frequency stability of CPT clocks. The experimental verification is performed both with a distributed-Bragg-reflector (DBR) laser and a vertical-cavity surface-emitting laser (VCSEL). The latter has a particular importance for developing MACs. The results of experiments are in qualitative agreement with analytical theory based on a double $Λ$ scheme of atomic energy levels.

physics.atom-ph↗

arXiv2022

Level-crossing resonances on open atomic transitions in a buffered Cs vapor cell: Linewidth narrowing, high contrast and applications to atomic magnetometry

The ground-state Hanle effect (GSHE) in alkali-metal atomic vapors using a single circularly polarized wave underlies one of the most robust and simplest techniques in atomic magnetometry. This effect causes a narrow (subnatural-width) resonance in the light wave intensity transmitted through a vapor cell. Usually, GSHE-based sensors operate in the spin-exchange-relaxation-free (SERF) regime. However, this regime requires a relatively high temperature of vapors (150 C or higher), leading to a relatively large heat release and power consumption of the sensor head. Besides, without applying special measures, SERF regime significantly limits a dynamic range of measurements. Here, we study a pump-probe scheme involving a single elliptically polarized wave and a polarimetric detection technique. The wave is in resonance with two adjacent optical transitions in the cesium D1 line (894.6 nm) owing to their overlapping in presence of a buffer gas (Ne, 130 Torr). Using a small (0.1 cm$^3$) glass vapor cell, we demonstrate a possibility of observing subnatural-width resonances with a high contrast-to-width ratio (up to 45 %/mG) under a low-temperature (60 C) regime of operation thanks to a strong light-induced circular dichroism. Basing on a $Λ$ scheme of atomic energy levels, we obtain explicit analytical expressions for the line shape. The model reveals a linewidth narrowing effect due to openness of the scheme. This result is unusual for magneto-optical atomic spectroscopy because the openness is commonly considered as a undesirable effect, degrading the resonance characteristics. We estimate a sensitivity of 1.8 pT/$\surd$Hz with a 60 fT/$\surd$Hz sensitivity in the photon-shot-noise limit. The results contribute to the theory of GSHE resonances and can be applied to development of a low-temperature high-sensitivity miniaturized magnetic field sensor with an extended dynamic range.

physics.atom-ph↗

arXiv2021

High-quality level-crossing resonances under counterpropagating circularly polarized light waves for applications in atomic magnetometry

Level-crossing (LC) resonances in a buffer-gas-filled cesium vapor cell are studied under counterpropagating pump and probe light waves with opposite circular polarizations. The waves excite the D$_1$-line ground-state level $F_g$$=\,$$4$, while a transverse magnetic field (${\rm B}_x$$\perp$${\rm k}$) is scanned around zero to observe the resonance of electromagnetically induced absorption (EIA). It is shown that adding the pump light wave significantly improves the properties of the resonances in comparison with the commonly used scheme with a single light wave. As far as a small vapor cell ($\approx\,$0.1 cm$^3$) at relatively low temperature ($\approx\,$45-60$\,^\circ$C) is utilized, the results have good prospects for developing a low-power miniaturized atomic magnetometer.

physics.atom-ph↗

arXiv2015

Quantum treatment of two-stage sub-Doppler laser cooling of magnesium atoms

The problem of deep laser cooling of $^{24}$Mg atoms is theoretically studied. We propose two-stage sub-Doppler cooling strategy using electro-dipole transition $3^3P_2$$\to$$3^3D_3$ ($λ$=383.9 nm). The first stage implies exploiting magneto-optical trap with $σ^+$ and $σ^-$ light beams, while the second one uses a lin$\perp$lin molasses. We focus on achieving large number of ultracold atoms (T$_{eff}$ < 10 $μ$K) in a cold atomic cloud. The calculations have been done out of many widely used approximations and based on quantum treatment with taking full account of recoil effect. Steady-state average kinetic energies and linear momentum distributions of cold atoms are analysed for various light-field intensities and frequency detunings. The results of conducted quantum analysis have revealed noticeable differences from results of semiclassical approach based on the Fokker-Planck equation. At certain conditions the second cooling stage can provide sufficiently lower kinetic energies of atomic cloud as well as increased fraction of ultracold atoms than the first one. We hope that the obtained results can assist overcoming current experimental problems in deep cooling of $^{24}$Mg atoms by means of laser fields. Cold magnesium atoms, being cooled in large number down to several microkelvins, have certain interest, for example, in quantum metrology.

physics.atom-ph↗

arXiv2014

Magneto-optical resonance of electromagnetically induced absorption with high contrast and narrow width in a vapour cell with buffer gas

The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counterpropagating light waves is proposed. We theoretically analyze the absorption of a probe light wave in presence of counterpropagating one with the same frequency as the function of a static magnetic field applied along the vectors of light waves, propagating in a vapour cell. Here, as an example, we study a "dark" type of atomic dipole transition Fg=1-->Fe=1 in D1 line of 87Rb, where usually the electromagnetically induced transparency (EIT) can be observed. To obtain the EIA signal one should proper chose the polarizations of light waves and intensities. In contrast of regular schemes for observing EIA signals (in a single travelling light wave in the Hanle configuration or in a bichromatic light field consisted of two travelling waves), the proposed scheme allows one to use buffer gas to significantly enhance properties of the resonance. Also the dramatic influence of atomic transition openness on contrast of the resonance is revealed, that gives great advantage in comparison with cyclic atomic transitions. The obtained results can be interesting in high-resolution spectroscopy, nonlinear and magneto-optics.

physics.atom-ph↗

arXiv2013

Nonlinear propagation of polarized light pulses in a medium of atoms with degenerate energy levels: adiabatic approach

We develop a general method allowing one to construct the consistent theory of light pulse propagation through an atomic medium in arbitrary nonlinear regime with respect to the field strength, taking into account the light polarization, temporal (frequency) and spatial dispersions. The method is based on the reduced Maxwell equation, atomic density matrix formalism and adiabatic approximation. In order to demonstrate the efficiency of our method we investigate in detail the case of propagation of the polarization pulse under conditions of coherent population trapping in a medium of two-level atoms with degenerate energy levels. Equations describing the evolution of various field parameters are derived. It is shown that pulses of ellipticity and spatial orientation of polarization ellipse propagate with slowing. Analytical expressions for the slowing factor are obtained. A previously unknown effects of the stimulated phase modulation and the generation of a phase pilot pulse by the variation of spatial orientation of the polarization ellipse are predicted. In addition, we show that the spatial dispersion can be interpreted as "wind effects".

physics.optics↗

arXiv2006

Electromagnetically induced absorption and transparency in magneto-optical resonances in elliptically polarized field

Using a 1 to 2 transition as an analytically tractable model, we discuss in detail magneto-optical resonances of both EIA (electromagnetically induced absorption) and EIT (electromagnetically induced transparency) types in the Hanle configuration. The analysis is made for arbitrary rate of depolarizing collisions in the excited state and arbitrary elliptical field polarization. The obtained results clearly show that the main reason for the EIA sub-natural resonance is the spontaneous transfer of anisotropy from the excited level to the ground one. In the EIA case we predict the negative structures in the absortpion resonance at large field detuning. The role of the finite atom-light interaction time is briefly discussed. In addition we study non-trivial peculiarities of the resonance lineshape related to the velocity spread in a gas.

quant-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↗