619 research outputs found
Strongly birefringent cut-wire pair structure as negative index wave plates at THz frequencies
We report a new approach for the design and fabrication of thin wave plates
with high transmission in the terahertz (THz) regime. The wave plates are based
on strongly birefringent cut-wire pair metamaterials that exhibit refractive
indices of opposite signs for two orthogonal polarization components of an
incident wave. As specific examples, we fabricated and investigated a quarter-
and a half-wave plate that revealed a peak intensity transmittance of 74% and
58% at 1.34 THz and 1.3 THz, respectively. Furthermore, the half wave plate
displayed a maximum figure of merit (FOM) of 23 at 1.3 THz where the refractive
index was -1.7. This corresponds to one of the highest FOMs reported at THz
frequencies so far. The presented results evidence that negative index
materials enter an application stage in terms of optical components for the THz
technology.Comment: 4 pages, 3 figures, submitted to Appl. Phys. Let
Measurement of the scalar third-order electric polarizability of the Cs ground state using coherent-population-trapping spectroscopy in Ramsey geometry
The ac-Stark shift induced by blackbody radiation is a major source of systematic uncertainty in present-day cesium microwave frequency standards. The shift is parametrized in terms of a third-order electric polarizability α(3)0 that can be inferred from the static electric-field displacement of the clock transition resonance. In this paper, we report on an all-optical coherent-population-trapping pump-probe experiment measuring the differential polarizability Îα(3)0=α(3)0(F=4)âα(3)0(F=3) on a thermal Cs atomic beam, from which we infer α(3)0(F=4)=2.023(6)stat(9)systHz/(kV/cm)2, which corresponds to a scalar Stark shift parameter ks=â2.312(7)stat(10)systHz/(kV/cm)2. The result agrees within two standard deviations with a recent measurement in an atomic fountain, and rules out another recent result obtained in a Cs vapor cell
CPT-pump-probe measurement of the Cs clock transition DC Stark shift
We report progress in measuring the third order electric polarizability of the Cs ground states using a Ramsey pump-probe experiment on coherent population trapped (CPT) atoms in a thermal atomic beam. We give a short description of the apparatus as well as the Fourier transform method used to monitor the phase and frequency of the Ramsey signal. Analysis of a typical data set is shown, proving the consistency of the method. We show that the motional magnetic field phase shift can be used to test the reliability of the electric field modeling. Finally, we give a preliminary value for the Cs ground state polarizability and compare it to previous published values of the DC Stark shift
Channeled scablands of eastern Washington: the geologic story of the Spokane flood
This booklet describes the formation of the Channeled Scablands by a series of glacial floods. It includes photographs of formations formed by the activity described in the text.
This work was originally published in 1947 by the Government Printing Office for the Department of the Interior with SuDoc number (I 19.2:W 27/6/974).https://dc.ewu.edu/spc_pubs/1005/thumbnail.jp
BĂșs dĂŒledĂ©keiden. HozzĂĄszĂłlĂĄs Halmai TamĂĄs ,MƱveltsĂ©g nĂ©lkĂŒli nemzedĂ©kek?â cĂmƱ ĂrĂĄsĂĄhoz
Expanded data presented in Supporting Information F is available here in text file format: âSIF2.Data.txtâ (Supporting Information F2)
Sensitivity of double resonance alignment magnetometers
We present an experimental study of the intrinsic magnetometric sensitivity
of an optical/rf-frequency double resonance magnetometer in which linearly
polarized laser light is used in the optical pumping and detection processes.
We show that a semi-empirical model of the magnetometer can be used to describe
the magnetic resonance spectra. Then, we present an efficient method to predict
the optimum operating point of the magnetometer, i.e., the light power and rf
Rabi frequency providing maximum magnetometric sensitivity. Finally, we apply
the method to investigate the evolution of the optimum operating point with
temperature. The method is very efficient to determine relaxation rates and
thus allowed us to determine the three collisional disalignment cross sections
for the components of the alignment tensor. Both first and second harmonic
signals from the magnetometer are considered and compared
Breaking the VE-cadherin bonds
Exchanges between the blood compartment and the surrounding tissues require a
tight regulation by the endothelial barrier. Recent reports inferred that
VE-cadherin, an endothelial specific cell-cell adhesion molecule, plays a
pivotal role in the formation, maturation and remodeling of the vascular wall.
Indeed, a growing number of permeability inducing factors (PIFs) was shown to
elicit signaling mechanisms culminating in VE-cadherin destabilization and
global alteration of the junctional architecture. Conversely, anti-PIFs protect
from VE-cadherin disruption and enhance cell cohesion. These findings provide
evidence on how endothelial cell-cell junctions impact the vascular network,
and change our perception about normal and aberrant angiogenesis
Experimental study of laser detected magnetic resonance based on atomic alignment
We present an experimental study of the spectra produced by
optical/radio-frequency double resonance in which resonant linearly polarized
laser light is used in the optical pumping and detection processes. We show
that the experimental spectra obtained for cesium are in excellent agreement
with a very general theoretical model developed in our group and we investigate
the limitations of this model. Finally, the results are discussed in view of
their use in the study of relaxation processes in aligned alkali vapors.Comment: 8 pages, 9 figures. Submitted to Phys. Rev. A. Related to
physics/060523
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