11,495 research outputs found
Coherent population trapping with polarization modulation
Coherent population trapping (CPT) is extensively studied for future vapor
cell clocks of high frequency stability. In the constructive polarization
modulation CPT scheme, a bichromatic laser field with polarization and phase
synchronously modulated is applied on an atomic medium. A high contrast CPT
signal is observed in this so-called double-modulation configuration, due to
the fact that the atomic population does not leak to the extreme Zeeman states,
and that the two CPT dark states, which are produced successively by the
alternate polarizations, add constructively. Here we experimentally investigate
CPT signal dynamics first in the usual configuration, a single circular
polarization. The double-modulation scheme is then addressed in both cases: one
pulse Rabi interaction and two pulses Ramsey interaction. The impact and the
optimization of the experimental parameters involved in the time sequence are
reviewed. We show that a simple sevenlevel model explains the experimental
observations. The double-modulation scheme yields a high contrast similar to
the one of other high contrast configurations like push-pull optical pumping or
crossed linear polarization scheme, with a setup allowing a higher compactness.
The constructive polarization modulation is attractive for atomic clock, atomic
magnetometer and high precision spectroscopy applications.Comment: 13 pages, 15 figures. To be published in Journ. Appl. Phys.(2016
Optical gyroscope system
Light beams pass in opposite directions through a single mode fiber optic wave guide that extends in a circle or coil in an optical gyroscope system which measures the rotation rate of the coil by measuring the relative phase shifts of the beams by interferometric techniques. Beam splitting and phase shifting of the light are facilitated by utilizing brief pulses of light and by using light-controlling devices which are operated for a brief time only when the light pulse passes in one direction through the device but not at a different time when the pulse is passing in the opposite direction through the device. High accuracy in rotation measurement is achieved at both very slow and very fast rotation rates, by alternately operating the system so that at zero rotation the interfering waves are alternately 90 out of phase and in phase. Linear polarization of the light beams is maintained by coiling the full length of the optic fiber in a single plane
Liquid Crystal Polarimetry for Metastability Exchange Optical Pumping of 3He
We detail the design and operation of a compact, discharge light polarimeter
for metastability exchange optical pumping of 3He gas near 1 torr under a low
magnetic field. The nuclear polarization of 3He can be discerned from its
electron polarization, measured via the circular polarization of 668 nm
discharge light from an RF excitation. This apparatus measures the circular
polarization of this very dim discharge light using a nematic liquid crystal
wave retarder (LCR) and a high-gain, transimpedance amplified Si photodiode. We
outline corrections required in such a measurement, and discuss contributions
to its systematic error
Ramsey spectroscopy of high-contrast CPT resonances with push-pull optical pumping in Cs vapor
We report the detection of high-contrast and narrow Coherent Population
Trapping (CPT) Ramsey fringes in a Cs vapor cell using a simple-architecture
laser system. The latter allows the combination of push-pull optical pumping
(PPOP) and a temporal Ramsey-like pulsed interrogation. An originality of the
optics package is the use of a single Mach-Zehnder electro-optic modulator (MZ
EOM) both for optical sidebands generation and light switch for pulsed
interaction. Typical Ramsey fringes with a linewidth of 166 Hz and a contrast
of 33 % are detected in a cm-scale buffer-gas filled Cs vapor cell. This
technique could be interesting for the development of high-performance and low
power consumption compact vapor cell clocks based on CPT.Comment: 9 pages, 8 figure
Polarization control proposal for Shanghai deep ultraviolet free electron laser
In this paper, a fully coherent radiation option with controllable
polarization is proposed for Shanghai deep ultraviolet free electron laser
(FEL) test facility. Intensive start-to-end simulation suggests that, the two
crossed planar undulators which generate the horizontal and vertical linear
polarized FEL respectively, should be placed as close as possible for avoiding
the polarization performance degradation of the final combined FEL radiation.
With the existence of the phase-shifter between the two crossed radiators,
Fourier-Transform-Limited output radiation with 100 nJ order pulse energy, 5 ps
full pulse length and circular polarization degree above 90% could be achieved.Comment: 9 pages, 5 figures, 1 tabl
Prospects for the measurement of the electron electric dipole moment using YbF
We discuss an experiment underway at Imperial College London to measure the
permanent electric dipole moment (EDM) of the electron using a molecular beam
of YbF. We describe the measurement method, which uses a combination of laser
and radiofrequency resonance techniques to detect the spin precession of the
YbF molecule in a strong electric field. We pay particular attention to the
analysis scheme and explore some of the possible systematic effects which might
mimic the EDM signal. Finally, we describe technical improvements which should
increase the sensitivity by more than an order of magnitude over the current
experimental limit.Comment: 6 pages, 2 figure
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