122 research outputs found
Distinguishing coherent atomic processes using wave mixing
We are able to clearly distinguish the processes responsible for enhanced
low-intensity atomic Kerr nonlinearity, namely coherent population trapping and
coherent population oscillations in experiments performed on the Rb D1 line,
where one or the other process dominates under appropriate conditions. The
potential of this new approach based on wave mixing for probing coherent atomic
media is discussed. It allows the new spectral components to be detected with
sub-kHz resolution, which is well below the laser linewidth limit. Spatial
selectivity and enhanced sensitivity make this method useful for testing dilute
cold atomic samples.Comment: 9 pages, 5 figure
Development of Filters with Minimal Hydraulic Resistance for Underground Water Intakes
The development of modern structures of water wells filtering equipment with enhanced performance characteristics is a vital task. The purpose of this work was to create filters for taking water from underground sources that have high performance, long service life, quickly and economically replace or repair in case of performance loss. The selection of the filter device must be made taking into account all the geological features of the aquifers, the performance characteristics of the filter devices and the size of the future structure. Filter equipment designs for water intake wells have been developed in this study. These filters have low hydraulic resistance, high performance and are easy to repair. This article presents the dependency of flow inside the receiving part of the well, the dependence of filter resistance at various forms of the cross section of the filter wire and the selected optimal section. The paper proposes a method for selecting the optimal cross-section of the filter wire used in the manufacture of a water well filter. The proposed structures of easy-to-remove well filters with increased productivity allow replacing the sealed well filter with a new one easily, reducing capital and operating costs, and increasing the inter-repair periods of their operation. Based on the presented method, examples are given for selecting the parameters of the filter wire cross-section. The above calculations showed that the use of the hydraulic resistance criterion at the design stage of underground water intakes can significantly reduce the cost of well construction. Studies have found that the minimum hydraulic resistance to ensure maximum filter performance is achieved when using filter wire teardrop and elliptical shapes
Steep anomalous dispersion in coherently prepared Rb vapor
Steep dispersion of opposite signs in driven degenerate two-level atomic
transitions have been predicted and observed on the D2 line of 87Rb in an
optically thin vapor cell. The intensity dependence of the anomalous dispersion
has been studied. The maximum observed value of anomalous dispersion [dn/dnu ~=
-6x10^{-11}Hz^{-1}] corresponds to anegative group velocity V_g ~= -c/23000.Comment: 4 pages, 4 figure
Absorption resonance and large negative delay in Rb vapor with buffer gas
We observe a narrow, isolated, two-photon absorption resonance in Rb for
large one-photon detuning in the presence of a buffer gas. In the absence of
buffer gas, a standard Lambda configuration of two laser frequencies gives rise
to electromagnetically induced transparency (EIT) for all values of one-photon
detuning throughout the inhomogeneously (Doppler) broadened line. However, when
a buffer gas is added and the one-photon detuning is comparable to or greater
than the Doppler width, an absorption resonance appears instead of the usual
EIT resonance. We also observe large negative group delay (~ -300 us for a
Gaussian pulse propagating through the media with respect to a reference pulse
not affected by the media), corresponding to a superluminal group velocity v_g=
-c/(3.6x10^6)=-84 m/s.Comment: 4 pages, 5 figure
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.Comment: 5 page
Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas
We experimentally study the group time delay for a light pulse propagating
through hot Rb vapor in the presence of a strong coupling field in a
configuration. We demonstrate that the ultra-slow pulse propagation is
transformed into superluminal propagation as the one-photon detuning of the
light increases due to the change in the transmission resonance lineshape.
Negative group velocity as low as -c/10^6=-80 m/s is recorded. We also find
that the advance time in the regime of the superluminal propagation grows
linearly with increasing laser field power.Comment: 5 pages, 6 figure
Enhanced frequency up-conversion in Rb vapor
We demonstrate highly efficient generation of coherent 420nm light via
up-conversion of near-infrared lasers in a hot rubidium vapor cell. By
optimizing pump polarizations and frequencies we achieve a single-pass
conversion efficiency of 260% per Watt, significantly higher than in previous
experiments. A full exploration of the coherent light generation and
fluorescence as a function of both pump frequencies reveals that coherent blue
light is generated close to 85Rb two-photon resonances, as predicted by theory,
but at high vapor pressure is suppressed in spectral regions that do not
support phase matching or exhibit single-photon Kerr refraction. Favorable
scaling of our current 1mW blue beam power with additional pump power is
predicted.Comment: 6 pages, 4 figures. Modified to include referees' improvement
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