arXiv subjects

David Sarkisyan

Publications and source records attributed to David Sarkisyan.

At least 19 recordsLinked to original sources

arXiv2026

Observation of Magnetically-Induced atomic transitions of the Cs 6S$_{1/2} \rightarrow 7$P$_{3/2}$ line at 456 nm

It has recently been demonstrated that magnetically induced (MI) transitions, a class of transitions forbidden at zero magnetic field, of the Cs 6$^2$S$_{1/2} \rightarrow 6^2$P$_{3/2}$ (D$_2$) line, exhibit promising features for high-resolution physics applications in the near-infrared range. In this work, we study a group of seven MI transitions ($F_g = 3 \rightarrow F_e = 5$) of the Cs $6^2$S$_{1/2} \rightarrow 7^2$P$_{3/2}$ line at $\lambda = 456$ nm. The experimental measurements are in very good agreement with theoretical predictions based on the diagonalization of the Zeeman Hamiltonian. In magnetic fields ranging from $0.2-3$ kG, these transitions reach a maximum intensity above that of conventional transitions. Another noteworthy property is their large frequency shift, reaching approximately $17~\mathrm{GHz}$ with respect to the unperturbed hyperfine transitions in magnetic fields of about $3~\mathrm{kG}$. These interesting properties may prove useful for the realization of optical frequency references or magnetometers with sub-micron spatial resolution in the blue region of the spectrum.

physics.atom-ph↗

arXiv2026

Saturated absorption and electromagnetically induced transparency of residual rubidium in dense cesium vapor

In the sealed-off cesium vapor cell studied in this work, a residual rubidium fraction of approximately $\sim$1\% was observed. We investigate the optical response of these trace Rb atoms in a sealed 1~cm long Cs-filled vapor cell. Despite the low concentration, laser excitation at 795~nm allows the observation of saturated absorption and electromagnetically induced transparency (EIT) resonances. The surrounding Cs vapor effectively acts as a buffer medium, reducing the Rb atomic velocity and increasing the interaction time with the laser field, which improves the EIT signal. The experiments are performed in an all-sapphire cell that can be heated up to 500$^{\circ}$C without window blackening, unlike conventional glass cells. From the measured spectra, Cs--Rb collisional cross sections are estimated. These results show that residual atomic species in high-temperature vapor cells can be exploited for spectroscopic and nonlinear-optical studies.

physics.atom-ph↗

arXiv2026

Features of the van der Waals Interaction on the Cesium $6S_{1/2} \rightarrow 7P_{3/2}$ Transition in an Optical Nanocell

We report the first experimental study of the influence of a dielectric surface on the transmission spectrum of cesium atoms for the $6S_{1/2} \rightarrow 7P_{3/2}$ ($D_2$) transition in vapor cells with thicknesses in the range $50$-$250\,$nm. The measurements were performed using a homemade optical nanocell filled with atomic cesium and featuring a wedge-shaped gap between the inner surfaces of sapphire windows. For atom-surface distances below approximately $300$\,nm, a significant red shift of the atomic transition frequency is observed due to van der Waals (vdW) interactions with the dielectric surface. An additional red shift arises at high vapor pressures owing to Cs-Cs interactions, with a measured contribution of $15$\,MHz/Torr, which must be accounted for in order to correctly determine the vdW coefficient $C_3$. By recording transmission spectra of the nanocell at different thicknesses, we determine for the first time the vdW coefficient for the Cs $6S_{1/2} \rightarrow 7P_{3/2}$ transition, obtaining values in the range $C_3 \sim 2- 20$\,kHz\,$\mu$m$^3$. These results are of interest for fundamental studies of atom-surface interactions and are also relevant for the development of miniature sensors based on atomic vapors, in particular compact frequency references exploiting atomic transitions in the blue spectral region.

physics.atom-ph↗

arXiv2025

Doppler-free Selective Reflection spectroscopy of the $6s$ $^2S_{1/2} \to 7p$ $^2P_{3/2}$ transition of Cesium using a nanofabricated vapor cell

Selective Reflection (SR) spectroscopy of the $6s$ $^2S_{1/2} \rightarrow$ $7p$ $^2P_{3/2}$ electric dipole transition of Cesium ($λ~=~456$ nm) is performed for the first time using a nanometric-thin cell ($L=50 - 1500$~nm). We succesfully form narrow resonances corresponding to the $F_g = 3,4 \rightarrow F_e =2,3,4,5$ hyperfine transitions. All transitions are well spectrally resolved and the geometry of the cell allows us to obtain a strong 30 times narrowing of the Doppler width with a single beam pass. For lower thicknesses ($L < 400$~nm), we observe a red shift of the \ac{SR} lines which we attribute to atom-surface interactions, and provide estimates of the $C_3$ interaction coefficient. The SR signal reaches several percent of the incident radiation up to a saturation intensity of 100 mW/cm$^2$. SR is a convenient tool for laser spectroscopy of the hyperfine structure of atoms as well as for the study of Zeeman transitions in magnetic fields. Experimental measurements are in good agreement with theoretical calculations.

physics.atom-ph↗

arXiv2024

Blue laser induced bright red fluorescence in hot cesium vapor

We have observed laser-induced fluorescence using 456 nm laser radiation, resonant with the 6S1/2-7P3/2 transition in Cs atoms. It includes red emission lines in the range of 580-730 nm and a prominent line at 852 nm corresponding to the 6P3/2-6S1/2 transition. A T-shaped all-sapphire cell with a length of 1 cm, containing Cs atomic vapor and capable of being heated up to 500 oC, was used. The laser-induced fluorescence (LIF) power at 852 nm was investigated as a function of the cell temperature. The maximum LIF power was achieved at 130 oC, while a significant decrease was observed around 300 oC. At 130 oC, the Doppler-broadened LIF spectrum at 852 nm exhibited self-conversion, resulting in the formation of two distinct peaks within the spectrum. The LIF power at 852 nm was also studied as a function of the 456 nm radiation power. The Cs cell demonstrated potential as an efficient optical filter and down-converter, effectively transforming 456 nm radiation into 852 nm radiation.

physics.atom-ph↗

arXiv2024

Experimental Investigation of Electromagnetically Induced Transparency in Selective Reflection Spectra

We have investigated electromagnetically induced transparency in the spectrum of selective reflection at the interface of Rb atom vapors and a dielectric nanocell window. A nanocell with atomic vapor column thicknesses ranging from 150 to 1200 nm, as well as a 50~$μ$m thickness microcell were used. We have compared electromagnetically induced transparency observed for the cases of the selective reflection and transmission. It was demonstrated that for the thicknesses of below $\leq 1000$ nm selective reflection technique is more favorable. In contrast, for wider cells and microcells, using transmitted radiation as probe field is more effective.

physics.atom-ph↗

arXiv2024

Electromagnetically induced transparency with magnetically-induced $ΔF=0, m_F=0 \rightarrow m_F=0$ probe transition

Interest in magnetically induced (MI) transitions of alkali metal atoms is caused by the fact that their intensities can exceed the intensities of regular atomic transitions in a wide range of magnetic field (200 - 4000 G). The goal of this work was to form and study, for the first time, an electromagnetically induced transparency (EIT) resonance in a strong magnetic field using a probe radiation tuned to |Fg = F; mF = 0-> Fe = F; mF = 0> MI transition, which is forbidden in zero magnetic field. Two narrow-band linearly-polarized cw diode lasers were used to form a EIT resonance on a lambda-type system of Cs atomic D2 line in a strong transverse magnetic field (up to 1000 G). The resonance was formed in Cs atomic vapor nanocell with the atomic vapor column thickness of 850 nm.

physics.atom-ph↗

arXiv2024

Influence of buffer gas on the formation of $N$-resonances in rubidium vapors

The $N$-resonance process is an accessible and effective method for obtaining narrow (down to subnatural linewidth), and contrasted resonances, using two continuous lasers and an Rb vapor cell. In this article, we investigate the impact of buffer gas partial pressure on the contrast and linewidth of $N$-resonances formed in the $D_1$ line of an $^{85}$Rb thermal vapor. $N$-resonances are compared to usual EIT resonances, and we highlight their advantages and disadvantages. Several rounds of measurements were performed with five vapor cells, each containing Rb and Ne buffer gas with different partial pressures (ranging from 0 to 400 Torr). This reveals the existence of an optimum Ne partial pressure that yields the best contrast, for which we provide a qualitative description. We then study the behavior of the $N$-resonance components when a transverse magnetic field is applied to the vapor cell. The frequency shift of each component is well described by theoretical calculations.

physics.atom-ph↗

arXiv2023

Observation of magnetically-induced transition intensity redistribution in the onset of the hyperfine Paschen-Back regime

The Zeeman effect is an important topic in atomic spectroscopy. The induced change in transition frequencies and amplitudes finds applications in the Earth-field-range magnetometry. At intermediate magnetic field amplitude $B\sim B_0 = A_\text{hfs}/μ_B$, where $A_\text{hfs}$ is the magnetic dipole constant of the ground state, and $μ_B$ is the Bohr magneton ($B_0\approx 1.7$ kG for Cs), the rigorous rule $ΔF = 0, \pm1$ is affected by the coupling between magnetic sub-levels induced by the field. Transitions satisfying $ΔF = \pm2$, referred to as magnetically-induced transitions, can be observed. Here, we show that a significant redistribution of the Cs $6\text{S}_{1/2}\rightarrow 6\text{P}_{3/2}$ magnetically-induced transition intensities occurs with increasing magnetic field. We observe that the strongest transition in the group $F_g=3\rightarrow F_e=5$ ($σ^+$ polarization) for $B 3 B_0$. On the other hand, the strongest transition in the group $F_g=2\rightarrow F_e=4$ ($σ^-$ polarization) remains so for all our measurements with magnetic fields up to 9 kG. These results are in agreement with a theoretical model. The model predicts that similar observations can be made for all alkali metals, including Na, K and Rb atoms. Our findings are important for magnetometers utilizing the Zeeman effect above Earth field, following the rapid development of micro-machined vapor-cell-based sensors.

physics.atom-ph↗

arXiv2023

Formation of narrow atomic lines of Rb in the UV region using a magnetic field

Magnetically induced (MI) transitions (F${}_{g}$ = 1 $\rightarrow$ F${}_{e}$= 3) of ${}^{87}$Rb D${}_{2}$ line are among the most promising atomic transitions for applications in laser physics. They reach their maximum intensity in the 0.2--2 kG magnetic field range and are more intense than many conventional atomic transitions. An important feature of MI transitions is their large frequency shift with respect to the unperturbed hyperfine transitions which reaches $\sim$12 GHz in magnetic fields of $\sim$ 3 kG, while they are formed on the high-frequency wing of the spectrum and do not overlap with other transitions. Some important peculiarities have been demonstrated for the MI 5S${}_{1/2}$$\rightarrow$ 5P${}_{3/2}$ transitions ($λ$=780 nm). Particularly, it was shown that using a nanocell with thickness $L= 100$~nm it is possible to realize 1 $μ$m-spatial resolution which is important when determining magnetic fields with strong spatial gradient (of $>$~3G /$μ$m). Earlier, our studies have been performed for 5S${}_{1/2}$ $\rightarrow$ $n$P${}_{3/2}$ transition with $n = 5$, while it is also theoretically shown to be promising for the transitions with $n = 6, 7, 8$ and $9$, corresponding to the transition wavelengths of 420.2~nm, 358.7~nm, 334.9~nm and 322.8~nm, respectively.

physics.atom-ph↗

arXiv2023

Formation of strongly shifted EIT resonances using "forbidden" transitions of Cesium

Atomic transitions satisfying $F_e - F_g = ΔF = \pm 2$ (where $F_e$ stands for excited and $F_g$ stands for ground state) of alkali atoms have zero probability in zero magnetic field (they are so-called "forbidden" transitions) but experience a large probabilty increase in an external magnetic field. These transitions are called magnetically induced (MI) transitions. In this paper, we use for the first time the $σ^+$ ($Δm_F~=~+1$) MI transitions $F_g = 3 \rightarrow F_e = 5$ of {Cesium} as probe radiation to form EIT resonances in strong magnetic fields (1 - 3 kG) while the coupling radiation frequency is resonant with $F_g=4\rightarrow F_e=5$ $σ^+$ transitions. The experiment is performed using a nanometric-thin cell filled with Cs vapor and a strong permanent magnet. The thickness of the vapor column is 852 nm, corresponding to the Cs $D_2$ line transition wavelength. Due to the large frequency shift slope of the MI transitions ($\sim$ 4 MHz/G), it is possible to form contrasted and strongly frequency-shifted EIT resonances. Particularly, a strong 12 GHz frequency shift is observed when applying an external magnetic field of $\sim$ 3 kG. Preliminary calculations performed considering Doppler-broadened three level systems in a nanocell are in reasonable agreement with the experimental measurements.

physics.atom-ph↗

arXiv2022

Saturated absorption technique used in Potassium microcell for magnetic field sensing

It is demonstrated that the use of a Micrometric Thin $^{39}$K vapor Cell (MTC) and Saturated Absorption spectroscopy (SA) allows to form narrow atomic lines in transmission spectrum without unwanted Cross-Over (CO) resonances. Another important feature is the small characteristic magnetic field value $B_0 = A_{hf}/μ_B$ of $^{39}$K, significantly smaller than for Rb and Cs. As a consequence, decoupling of $J$ and $I$ can be observed at relatively low magnetic fields $\sim$300 G, which results in the formation of two groups of four well-spectrally-resolved and equidistantly-positioned atomic transitions having the same amplitude (each group corresponds to a given circular polarization $σ^\pm$) which we record using a simple experimental setup with a linearly polarized tunable diode-laser and a longitudinal magnetic field obtained with two permanent magnets. Fabrication of a MTC is much easier than the fabrication of the $^{39}$K nanocells used in our previous works. A simple method to determine the magnitude of a wide range of B-fields with a spatial resolution of 30 $μ$m is presented, which is intrinsically calibrated and does not require a frequency reference.

physics.atom-ph↗

arXiv2022

Coherent Optical Processes on Cs D$_2$ line Magnetically Induced Transitions

The increased spectral resolution allowed by the use of extremely thin vapor cells has led to the observation of interesting behaviour of alkali transitions when placed in a magnetic field. Particularly, transitions obeying an apparent $F_e-F_g\equivΔF =\pm2$ selection rule, referred to as magnetically-induced (MI) transitions, have their probabilities largely increase in the intermediate interaction regime while being null at zero and higher magnetic fields. With an 800 nm-thick Cs vapor cell placed in a field up to 1.5 kG, we show here that the generation of electromagnetically induced transparency (EIT), realized in $Λ$-systems involving $ΔF =- 2$ MI transitions, is only possible when both the coupling and probe beams are $σ^-$-circular polarized, demonstrating that EIT is affected by magnetic circular dichroism. A similar rule of thumb can be extrapolated for $ΔF =+2$ MI transitions and $σ^+$ polarization. Because of the high frequency shift slope (typ. 4 MHz/G), the generation of EIT resonances involving MI transitions is interesting, especially in the context of growing attention towards micro-machined alkali vapor cell sensors.

physics.atom-ph↗

arXiv2021

Strongest Magnetically Induced Transitions in Alkali Metal Atoms with nuclear spin $3/2$

The probabilities of atomic transitions $F_e - F_g = \pm 2$ between a ground $F_g$ and an excited $F_e$ level of $D_2$ line of any alkali metal atom are zero when no external magnetic field is applied. In an external magnetic field in the range $0.1 - 3$ kG, the probabilities of these transitions called magnetically induced (MI) are highly modified. For these MI transitions, we have previously exhibited the following rule: the probabilities of MI transitions with $ΔF = +2$ are maximal when using $σ^+$-polarized laser radiation, while the probabilities of MI transitions with $ΔF = -2$ are maximal when using $σ^-$-polarized laser radiation. This difference has been termed Type 1 Magnetically Induced Circular Dichroism (MCD1). It is demonstrated for the first time that for alkali atoms with a nuclear spin $I=3/2$ ($^{87}\text{Rb}$, $^{39}\text{K}$,$^{23}\text{Na}$, $^7\text{Li}$) in magnetic fields $> 100$ G, the probability of the strongest $σ^+$ MI transition of the group $F_g = 1 \rightarrow F_e = 3'$ (transition $\ket{1,-1}\rightarrow\ket{3',0'}$) is about 4 times higher than the probabilities of the strongest MI $σ^-$-transitions $\ket{1,-1}\rightarrow\ket{3',-2'}$ and $\ket{2,+1}\rightarrow \ket{0',0'}$. These properties make the $σ^+$ MI transition $\ket{1,-1}\rightarrow\ket{3',0'}$ an interesting candidate for the study of magneto-optical processes in strong magnetic fields.

physics.atom-ph↗

arXiv2020

Circular dichroism in atomic vapors: magnetically induced transitions responsible for two distinct behaviors

Atomic transitions of alkali metals for which the condition $F_e-F_g = \pm2$ is satisfied have null probability in a zero magnetic field, while a giant increase can occur when an external field is applied. Such transitions, often referred to as magnetically-induced (MI) transitions, have received interest because their high probabilities in wide ranges of external magnetic fields which, in some cases, are even higher than that of usual atomic transitions. Previously, the following rule was established: the intensities of MI transitions with $ΔF=\pm2$ are maximum when using respectively $σ^\pm$ radiation. Within the same ground state, the difference in intensity for $σ^+$ and $σ^-$ radiations can be significant, leading to magnetically induced circular dichroism (MCD), referred to as type-1. Here, we show that even among the strongest MI transitions, $i.e$ originating from different ground states for $σ^+$ and $σ^-$, the probability of MI transition with $ΔF = + 2$ is always greater, which leads to another type of MCD. Our experiments are performed with a Cs-filled nanocell, where the laser is tuned around the D$_2$ line; similar results are expected with other alkali metals. Theoretical calculations are in excellent agreement with the experimental measurements.

physics.atom-ph↗

arXiv2020

Features of Magnetically-induced atomic transitions of Rb D$_1$ line studied by Doppler-free method based on the second derivative of the absorption spectra

We show that the Second Derivative (SD) technique of the absorption spectra of Rb atomic vapours confined in a nanocell with a thickness $\ell= λ/2=398$ nm allows to achieve close to Doppler-free spectroscopy. Narrow linewidth and linearity of the SD signal response with respect to transition probabilities allow us to study separately, in an external transverse magnetic field (0.6 to 4 kG), a big number of the atomic transitions of $^{85}$Rb and $^{87}$Rb atoms. Atomic transitions $|F_g,0\rangle \rightarrow |F_e=F_g,0'\rangle$, for which the dipole moment is null at zero magnetic field (so-called magnetically-induced transitions), show a gigantic increase in probability with increasing magnetic field. When a magnetic field is applied on the vapour, we show the possibility of forming a dark resonance on these transitions by adding a coupling laser. We hence demonstrate a five-fold increase in the transmission of the probe radiation when the coupling laser is on. Theoretical calculations are in a very good agreement with experimental results.

physics.atom-ph↗

arXiv2019

Proof of the feasibility of a nanocell-based wide-range optical magnetometer

We present an experimental scheme performing scalar magnetometry based on the fitting of Rb D$_2$ line spectra recorded by derivative selective reflection spectroscopy from an optical nanometric-thick cell. To demonstrate its efficiency, the magnetometer is used to measure the inhomogeneous magnetic field produced by a permanent neodimuim-iron-boron alloy ring magnet at different distances. The computational tasks are realized by relatively cheap electronic components: an Arduino Due board for the external control of the laser and acquisition of spectra, and a Raspberry Pi computer for the fitting. The coefficient of variation of the measurements remains under $5\%$ in the magnetic field range of 40 - 200 mT, limited only by the size of the oven and translation stage used in our experiment. The proposed scheme is expected to operate with a high measurement precision also for stronger magnetic fields ($>500~$mT), in the hyperfine Paschen-Back regime, where the evolution of the atomic transitions can be calculated with a high accuracy.

physics.atom-ph↗

arXiv2019

Resolution-enhanced quantitative spectroscopy of atomic vapor in optical nanocells based on second-derivative processing of spectra

We present a method for recovery of narrow homogeneous spectral features out of broad inhomogeneous overlapped profile based on second-derivative processing of the absorption spectra of alkali metal atomic vapor nanocells. The method is shown to preserve the frequency positions and amplitudes of spectral transitions, thus being applicable for quantitative spectroscopy. The proposed technique was successfully applied and tested for: measurements of hyperfine splitting and atomic transition probabilities; development of an atomic frequency reference; determination of isotopic abundance; study of atom-surface interaction; and determination of magnetic field-induced modification of atomic transitions frequency and probability. The obtained experimental results are fully consistent with theoretical modeling.

physics.atom-ph↗