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Search Results: 1 - 10 of 43 matches for " Marcis Auzinsh "
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Validity of Rate Equations for Zeeman Coherences for Analysis of Nonlinear Interaction of Atoms with Laser Radiation
Kaspars Blushs,Marcis Auzinsh
Physics , 2003, DOI: 10.1103/PhysRevA.69.063806
Abstract: In this paper we, to our knowledge, for the first time obtain the rate equations for Zeeman coherences in the broad line approximation and steady-state balance equations directly from optical Bloch equations without the use of the perturbation theory. The broad line approximation allows us to use the adiabatic elimination procedure in order to eliminate the optical coherences from the optical Bloch equations, but the steady-state condition allows us to derive the balance equations straightforward. We compare our approach with the perturbation theory approach as given previously and show that our approach is more flexible in analyzing various experiments. Meanwhile we also show the validity and limitations of the application of the rate equations in experiments with coherent atomic excitation, when either broad line approximation or steady-state conditions hold. Thus we have shown the basis for modeling the coherent atomic excitation experiments by using the relatively simple rate equations, provided that certain experimental conditions hold.
Angular momentum spatial distribution symmetry breaking in Rb by an external magnetic field
Janis Alnis,Marcis Auzinsh
Physics , 2000, DOI: 10.1103/PhysRevA.63.023407
Abstract: Excited state angular momentum alignment -- orientation conversion for atoms with hyperfine structure in presence of an external magnetic field is investigated. Transversal orientation in these conditions is reported for the first time. This phenomenon occurs under Paschen Back conditions at intermediate magnetic field strength. Weak radiation from a linearly polarized diode laser is used to excite Rb atoms in a cell. The laser beam is polarized at an angle of pi/4 with respect to the external magnetic field direction. Ground state hyperfine levels of the 5S_1/2 state are resolved using laser-induced fluorescence spectroscopy under conditions for which all excited 5P_3/2 state hyperfine components are excited simultaneously. Circularly polarized fluorescence is observed to be emitted in the direction perpendicular to both to the direction of the magnetic field B and direction of the light polarization E. The obtained circularity is shown to be in quantitative agreement with theoretical predictions.
Reversed Dark Resonance in Rb Atom Excited by a Diode Laser
Janis Alnis,Marcis Auzinsh
Physics , 2000, DOI: 10.1088/0953-4075/34/20/302
Abstract: Origin of recently discovered reversed (opposite sign) dark resonances was explained theoretically and verified experimentally. It is shown that the reason for these resonances is a specific optical pumping of ground state level in a transition when ground state angular momentum is smaller than the excited state momentum.
Manipulation of Dark States and Control of Coherent Processes with Spectrally Broad Light
Marcis Auzinsh,Nikolai Bezuglov,Kaspars Miculis
Physics , 2008, DOI: 10.1103/PhysRevA.78.053415
Abstract: The formation of dark states under interaction of degenerate atomic states with incoherent broadband radiation (white light) is discussed. A simple coupling scheme in a three level Lambda-system, which allows both qualitative and quantitative analysis is discussed. We found a stationary solution of the optical Bloch equations in a broad excitation line approximation that describes the dynamics of the atom-white light interaction and demonstrated its identity to a conventional dark state created with coherent laser fields. We than examine the efficiency of the population transfer induced by broadband radiation in a model Lambda-system and revealed that high efficiency (attaining 100 percent) of stimulated Raman adiabatic passage-like processes can be achieved with certain temporal control of light polarization. The corresponding criterion of adiabaticity was formulated and justified by means of numerical simulations.
F-resolved Magneto-optical Resonances at D1 Excitation of Cesium: Experiment and Theory
Marcis Auzinsh,Ruvin Ferber,Florian Gahbauer,Andrey Jarmola,Linards Kalvans
Physics , 2008, DOI: 10.1103/PhysRevA.78.013417
Abstract: Bright and dark nonlinear magneto-optical resonances associated with the ground state Hanle effect have been studied experimentally and theoretically for D1 excitation of atomic cesium. This system offers the advantage that the separation between the different hyperfine levels exceeds the Doppler width, and, hence, transitions between individual levels can be studied separately. Experimental measurements for various laser power densities and transit relaxation times are compared with a model based on the optical Bloch equations, which averages over the Doppler contour of the absorption line and simultaneously takes into account all hyperfine levels, as well as mixing of magnetic sublevels in an external magnetic field. In contrast to previous studies, which could not resolve the hyperfine transitions because of Doppler broadening, in this study there is excellent agreement between experiment and theory regarding the sign (bright or dark), contrast, and width of the resonance. The results support the traditional theoretical interpretation, according to which these effects are related to the relative strengths of transition probabilities between different magnetic sublevels in a given hyperfine transition.
Spatial dynamics of laser-induced fluorescence in an intense laser beam: experiment and theory in alkali metal atoms
Marcis Auzinsh,Andris Berzins,Ruvin Ferber,Florian Gahbauer,Uldis Kalnins
Physics , 2015,
Abstract: We have shown that it is possible to model accurately optical phenomena in intense laser fields by taking into account the intensity distribution over the laser beam. We developed a theoretical model that divided an intense laser beam into concentric regions, each with a Rabi frequency that corresponds to the intensity in that region, and solved a set of coupled optical Bloch equations for the density matrix in each region. Experimentally obtained magneto-optical resonance curves for the $F_g=2\longrightarrow F_e=1$ transition of the $D_1$ line of $^{87}$Rb agreed very well with the theoretical model up to a laser intensity of around 200 mW/cm$^2$ for a transition whose saturation intensity is around 4.5 mW/cm$^2$. We have studied the spatial dependence of the fluorescence intensity in an intense laser beam experimentally and theoretically. An experiment was conducted whereby a broad, intense pump laser excited the $F_g=4\longrightarrow F_e=3$ transition of the $D_2$ line of cesium while a weak, narrow probe beam scanned the atoms within the pump beam and excited the $D_1$ line of cesium, whose fluorescence was recorded as a function of probe beam position. Experimentally obtained spatial profiles of the fluorescence intensity agreed qualitatively with the predictions of the model.
A method for the quantitative study of atomic transitions in a magnetic field based on an atomic vapor cell with L=lambda
Armen Sargsyan,Grant Hakhumyan,Aram Papoyan,David Sarkisyan,Aigars Atvars,Marcis Auzinsh
Physics , 2008,
Abstract: We describe the so-called "Lambda-Zeeman method" to investigate individual hyperfine transitions between Zeeman sublevels of atoms in an external magnetic field of 0.1 mT - 0.25 T. Atoms are confined in a nanocell with thickness L = Lambda, where Lambda is the resonant wavelength (794 nm or 780 nm for D1 or D2 line of Rb). Narrow resonances in the transmission spectrum of the nanocell are split into several components in a magnetic field; their frequency positions and probabilities depend on the B-field. Possible applications are described, such as magnetometers with nanometric spatial resolution and tunable atomic frequency references.
Sub-Doppler spectroscopy of Rb atoms in a sub-micron vapor cell in the presence of a magnetic field
David Sarkisyan,Aram Papoyan,Tigran Varzhapetyan,Janis Alnis,Kaspars Blush,Marcis Auzinsh
Physics , 2003, DOI: 10.1088/1464-4258/6/3/023
Abstract: We report the first use of an extremely thin vapor cell (thickness ~ 400 nm) to study the magnetic-field dependence of laser-induced-fluorescence excitation spectra of alkali atoms. This thin cell allows for sub-Doppler resolution without the complexity of atomic beam or laser cooling techniques. This technique is used to study the laser-induced-fluorescence excitation spectra of Rb in a 50 G magnetic field. At this field strength the electronic angular momentum J and nuclear angular momentum I are only partially decoupled. As a result of the mixing of wavefunctions of different hyperfine states, we observe a nonlinear Zeeman effect for each sublevel, a substantial modification of the transition probabilities between different magnetic sublevels, and the appearance of transitions that are strictly forbidden in the absence of the magnetic field. For the case of right- and left- handed circularly polarized laser excitation, the fluorescence spectra differs qualitatively. Well pronounced magnetic field induced circular dichroism is observed. These observations are explained with a standard approach that describes the partial decoupling of I and J states.
Magnetic field-induced mixing of hyperfine states of Cs 6 2^P_{3/2} level observed with a sub-micron vapor cell
Aram Papoyan,David Sarkisyan,Kaspars Blush,Marcis Auzinsh,Daniel Bloch,Martial Ducloy
Physics , 2003,
Abstract: The fluorescence spectra of a sub-micron atomic cesium vapor layer observable under resonant excitation on D2 line have been studied in the presence of an external magnetic field. Substantial changes in amplitudes and frequency positions of the individual (resolved) hyperfine transitions have been recorded in moderate magnetic fields (up to ~ 50 Gauss). These features are caused by mixing of the hyperfine states of the upper level resulting from comparable values of the hyperfine splitting of the 62^P_{3/2} manifold and Larmor frequencies of the magnetic sublevels. The results of simulation show a good agreement with the experimental spectra. Possible application of the results for high spatial resolution magnetometry is discussed.
Conversion of bright magneto-optical resonances into dark at fixed laser frequency for D2 excitation of atomic rubidium
Marcis Auzinsh,Andris Berzins,Ruvin Ferber,Florian Gahbauer,Linards Kalvans,Arturs Mozers,Dmitrijs Opalevs
Physics , 2011, DOI: 10.1103/PhysRevA.85.033418
Abstract: Nonlinear magneto-optical resonances on the hyperfine transitions belonging to the D2 line of rubidium were changed from bright to dark resonances by changing the laser power density of the single exciting laser field or by changing the vapor temperature in the cell. In one set of experiments atoms were excited by linearly polarized light from an extended cavity diode laser with polarization vector perpendicular to the light's propagation direction and magnetic field, and laser induced fluorescence (LIF) was observed along the direction of the magnetic field, which was scanned. A low-contrast bright resonance was observed at low laser power densities when the laser was tuned to the Fg=2 --> Fe=3 transition of Rb-87 and near to the Fg=3 --> Fe=4 transition of Rb-85. The bright resonance became dark as the laser power density was increased above 0.6mW/cm2 or 0.8 mW/cm2, respectively. When the Fg=2 --> Fe=3 transition of Rb-87 was excited with circularly polarized light in a second set of experiments, a bright resonance was observed, which became dark when the temperature was increased to around 50C. The experimental observations at room temperature could be reproduced with good agreement by calculations based on a theoretical model, although the theoretical model was not able to describe measurements at elevated temperatures, where reabsorption was thought to play a decisive role. The model was derived from the optical Bloch equations and included all nearby hyperfine components, averaging over the Doppler profile, mixing of magnetic sublevels in the external magnetic field, and a treatment of the coherence properties of the exciting radiation field.
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