1,217 research outputs found
Observation of polarization quantum noise of laser radiation in Rb vapor cell
We present experimental study of polarization quantum noise of laser
radiation passed through optically think vapor of Rb87. We observe a step-like
noise spectrum. We discuss various factor which may result in such noise
spectrum and prevent observation of squeezing of quantum fluctuations predicted
in Matsko et al. PRA 63, 043814 (2001).Comment: 4 pages, 5 figures. Translated from Russian by I. Novikov
Temperature dependence of the electron spin g factor in GaAs
The temperature dependence of the electron spin factor in GaAs is
investigated experimentally and theoretically. Experimentally, the factor
was measured using time-resolved Faraday rotation due to Larmor precession of
electron spins in the temperature range between 4.5 K and 190 K. The experiment
shows an almost linear increase of the value with the temperature. This
result is in good agreement with other measurements based on photoluminescence
quantum beats and time-resolved Kerr rotation up to room temperature. The
experimental data are described theoretically taking into account a diminishing
fundamental energy gap in GaAs due to lattice thermal dilatation and
nonparabolicity of the conduction band calculated using a five-level kp model.
At higher temperatures electrons populate higher Landau levels and the average
factor is obtained from a summation over many levels. A very good
description of the experimental data is obtained indicating that the observed
increase of the spin factor with the temperature is predominantly due to
band's nonparabolicity.Comment: 6 pages 4 figure
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The New Normal: The Resurgence of Activist Investing Since the End of the Financial Crisis
ince 2010 there has been an incredible inflow of capital to hedge funds that focus specifically on activist investing. The aggressive and often hostile actions of activist funds have created negative publicity and an increased focus on the shortened holding period of these investors. But are activists a blessing or a curse?
This report, produced by the M&A Research Centre (MARC) at Cass Business School provides an insight into the short- and long-term performance effects of activist campaigns in the United States, Germany, and the United Kingdom since the financial crisis.
This report should not be considered as a guide for activist investors on what tactics to use or a guide for company executives on what they should be prepared for. It rather highlights important patterns in the outcomes of shareholder activism in the United States, Germany, and United Kingdom since the beginning of 2010, when the economies of these countries were emerging from the depths of the financial crisis.
Activism tends to be concentrated largely in the United States, but the expectations for further expansion into Europe make it important to understand its existing environment and what activist methods have had success in the region. As equity markets reach new heights in Europe, there will be new opportunities for activist investors
Slow light in paraffin-coated Rb vapor cells
We present preliminary results from an experimental study of slow light in
anti-relaxation-coated Rb vapor cells, and describe the construction and
testing of such cells. The slow ground state decoherence rate allowed by coated
cell walls leads to a dual-structured electromagnetically induced transparency
(EIT) spectrum with a very narrow (<100 Hz) transparency peak on top of a broad
pedestal. Such dual-structure EIT permits optical probe pulses to propagate
with greatly reduced group velocity on two time scales. We discuss ongoing
efforts to optimize the pulse delay in such coated cell systems.Comment: 6 pages, 6 figures, submitted to Journal of Modern Optic
EIT and diffusion of atomic coherence
We study experimentally the effect of diffusion of Rb atoms on
Electromagnetically Induced Transparency (EIT) in a buffer gas vapor cell. In
particular, we find that diffusion of atomic coherence in-and-out of the laser
beam plays a crucial role in determining the EIT resonance lineshape and the
stored light lifetime.Comment: 5 pages, 8 figure
Dynamic optical bistability in resonantly enhanced Raman generation
We report observations of novel dynamic behavior in resonantly-enhanced
stimulated Raman scattering in Rb vapor. In particular, we demonstrate a
dynamic hysteresis of the Raman scattered optical field in response to changes
of the drive laser field intensity and/or frequency. This effect may be
described as a dynamic form of optical bistability resulting from the formation
and decay of atomic coherence. We have applied this phenomenon to the
realization of an all-optical switch.Comment: 4 pages, 5 figure
Optimal control of light pulse storage and retrieval
We demonstrate experimentally a procedure to obtain the maximum efficiency
for the storage and retrieval of light pulses in atomic media. The procedure
uses time reversal to obtain optimal input signal pulse-shapes. Experimental
results in warm Rb vapor are in good agreement with theoretical predictions and
demonstrate a substantial improvement of efficiency. This optimization
procedure is applicable to a wide range of systems.Comment: 5 pages, 4 figure
Adsorption mechanisms of palladium on the Tobacco Mosaic Virus surface
Organic-inorganic materials synthesis using biological templates has recently drawn immense attention of researchers. Biotemplating has shown to be an efficient and economic means of nanomaterials production. Naturally stable, readily available and genetically malleable, Tobacco Mosaic Virus (TMV) is one of the most extensively studied and characterized biotemplates. Particularly, templated synthesis using TMV has produced high quality nanorods and nanowires that have been applied to batteries, memory devices and catalysis. The fundamental mechanisms, governing the adsorption of palladium on the TMV Wild Type and genetically modified versions (TMV1Cys and TMV2Cys), are not fully understood; this knowledge, however, is essential for future controllable synthesis. We are using UV Vis spectrometer to track the absorbance of palladium species in the solution in order to model the mechanism of adsorption on TMV surfaces using Freundlich and Langmuir isotherms. The mechanism is studied at 25 degrees Celsius at various palladium incubation concentrations. Adsorption on TMV Wild Type and TMV1Cys was successfully characterized by Langmuir isotherm, while adsorption on TMV2Cys, however, was found to be well characterized by Freundlich isotherm. With these models we were able to quantify the maximum capacities and adsorption intensities for TMV Wild Type and its mutants. Therefore, we were able to mathematically describe the differences in adsorption caused by the presence of thiol groups on the surface of TMV
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