1,720,993 research outputs found
Light-induced atomic desorption in cells with different PDMS coatings
Full text linkLight-induced atomic desorption (LIAD) is a non-thermal process in which atoms adsorbed at a surface are released under illumination. It is applied mostly for realization of optical dispensers in the cases when high atomic density at low temperature is needed – for example, for loading atomic devices as atomic magnetometers, atomic clocks, magneto-optical traps and their miniaturization. However as desorption depends on the atom-surface interaction it can be applied for optical characterization and manipulation of alkali metal nanoparticles as well. In this work an experimental investigation of the shape of the transmission spectra and their dependence on the illuminating blue light power in PDMS coated cells prepared with two different concentrations of PDMS to ether is presented. Comparison with the LIAD effect in SC-77 coated and uncoated cells is done. All measurements are on the Rb D2 line in vacuum. The potential for application of these dependences for analysis of the quality of the coating surface and its optimisation is discussed
Transformation of electromagnetically induced transparency into absorption in a thermal potassium optical cell with spin preserving coating
Full text linkWe report a new experimental approach where an order of magnitude enhancement of the electromagnetically induced absorption (EIA) resonance contrast, thus making it similar to that of the EIT resonance contrast is observed under the same conditions. The EIA signal results from the interaction of a weak probe beam with a ground state that has been driven by the pump (counter-propagating) beam. Probe absorption spectra are presented where the laser frequency is slowly detuned over the D 1 line of 39 K vapor contained in a cell with a PDMS antirelaxation coating. In addition to the frequency detuning, a magnetic field orthogonal to the laser beams is scanned around zero value at a higher rate. With both laser beams linearly polarized, an EIT resonance is observed. However, changing the pump beam polarization from linear to circular reverses the resonance signal from EIT to EIA
Optical characterization of antirelaxation coatings
Full text linkAntirelaxation coatings (ARC) are used in optical cells containing alkali metal vapor to reduce the depolarization of alkali atoms after collisions with the cell walls. The long-lived ground state polarization is a basis for development of atomic clocks, magnetometers, quantum memory, slow light experiments, precision measurements of fundamental symmetries etc. In this work, a simple method for measuring the number of collisions of the alkali atoms with the cell walls without atomic spin randomization (Nasyrov et al., Proc. SPIE (2015)) was applied to characterize the AR properties of two PDMS coatings prepared from different solutions in ether (PDMS 2% and PDMS 5%). We observed influence of the light-induced atomic desorption (LIAD) on the AR properties of coatings
Coherent population trapping resonances in Cs atoms excited by elliptically polarized light
No full textCoherent population trapping CPT resonances study in Hanle configuration is reported for different polarizations
of the exciting light field, on the D2 line of Cs atoms. While for linear/circular polarization dip/peak
in the fluorescence is registered, in case of elliptical polarization, a complex shape resonance is evidenced
experimentally, whose profile strongly depends on the ellipticity of polarization. A theoretical model is proposed
and developed, which includes the influence on the resonance of polarization ellipticity, transverse
magnetic field, and spatial intensity profile of the laser beam. Good agreement is found between the theoretical
and experimental results. The reported results allow one to accomplish more profound than in previous research
analysis of the CPT resonances behavior pointing out their sensitivity to the light polarization and power
as well as to transverse magnetic fields. The presented study is of general importance for the wide application
of the coherent resonances in high resolution spectroscopy and precise measurements. The purity of linear/
circular polarization of the light needed in different applications can be estimated implementing the proposed
model
Method and device for measurement of magnetic induction
No full textThe invention relates to an optical method and device for measurement of magnetic induction of small magnetic fields and small changes in magnetic fields of the order of ~ [mu]Gauss to ~ 10 Gauss based on Coherent Resonances at the Zeeman sublevels of a single hyperfine transition in alkali atoms. The atomic system is coherently excited by means of a laser source with a modulation of the light frequency with a frequency lower than 1 GHz. The modulation frequency at which the Coherent Resonances are registered is a measure of the induction of the existing magnetic field
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dual channel self-oscillating optical magnetometer
No full textWe report on a two-channel magnetometer based on nonlinear magneto-optical rotation in a Cs glass cell with buffer gas. The Cs atoms are optically pumped and probed by free running diode lasers tuned to the D2 line. A
wide frequency modulation of the pump laser is used to produce both synchronous Zeeman optical pumping and hyperfine repumping. The magnetometer works in an unshielded environment, and a spurious signal from distant magnetic sources is rejected by means of differential measurement. In this regime the magnetometer simultaneously gives the magnetic field modulus and the field difference. Rejection of the common-mode noise allows for high-resolution magnetometry with a sensitivity
of 2 pT/ Hz^(1/2). This sensitivity, in conjunction with long-term stability and a large bandwidth, makes it possible to detect water proton magnetization and its free induction decay in a measurement volume of 5 cm^3
Antirelaxation coatings in coherent spectroscopy: Theoretical investigation and experimental test
No full textWe describe a theoretical model, based on a density matrix and the Liouville equation, for the investigation of magneto-optical resonances in alkali-metal atomic vapor, in particular in the case of the electromagnetically induced transparency (EIT) in the presence of antirelaxation coatings. The influence of the coating is parametrized with an empirical coefficient describing its efficiency; the calculations are extended to a broad range of coating quality, contrary to previous works, and to uncoated cells. The model takes into account also different configurations for the EIT formation and different efficiency of optical pumping, as determined by the coating characteristics and the atomic energy structure. The model is validated by investigating the EIT with degenerate Zeeman levels in K39 D1 and Cs D2 lines, which exhibit respectively an almost negligible and a relevant impact of hyperfine optical pumping. The results are compared to experimental data, exhibiting good agreement; in particular, for the K39 D1 line, recent findings are shown here in the case of degenerate and nondegenerate EIT with amplitude-modulated light. Our results demonstrate an effective approach for the investigation of antirelaxation coatings and their contribution in the formation of magneto-optical resonances in alkali-metal atoms, in different regimes and with largely different efficiencies. This sheds new light on well-known but not yet entirely clarified phenomena and their behavior as a function of experimental parameters
Optical characterization of antirelaxation coatings for photonics applications
No full textOptical characterization of antirelaxation coatings with regard to their applications in coherent spectroscopy and LIAD experiments is presented. A simple method, based on the recording of the fluorescence intensity of the Rb alkali atoms during resonant light pulse irradiation is used for comparison of the antirelaxation properties of the coatings. The LIAD yield and dynamics are measured by registration of the 780 nm Rb line transmission. The comparison of the parameters of PDMS coatings prepared with two different solutions in ether (PDMS 2% and PDMS 5%) shows that when illuminating with such LED intensity at which the LIAD efficiency is equal in the two cells, the light induced Rb vapor density changes are about an order of magnitude slower in the PDMS 2% cell, and the antirelaxation properties of the two cells are equal
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