132 research outputs found
Towards optimization of pulsed sodium laser guide stars
Pulsed sodium laser guide stars (LGS) are useful because they allow for
Rayleigh blanking and fratricide avoidance in multiple-LGS systems.
Bloch-equation simulations of sodium-light interactions show that these may be
able to achieve photon returns nearly equal to, and in some cases greater than,
what is seen from continuous-wave (CW) excitation. In this work, we study the
time-dependent characteristics of sodium fluorescence, and investigate the
optimal format for the new fiber laser LGS that will be part of the upgraded
adaptive optics (AO) system on the Shane telescope at Mt. Hamilton. Results of
this analysis are examined in the context of their general applicability to
other LGS systems and the potential benefits of uplink correction are
considered. Comparisons of simulation predictions with measurements from
existing LGS are also presented and discussed.Comment: 9 pages, 7 figures, accepted by JOSA
Variable Free Spectral Range Spherical Mirror Fabry-Perot Interferometer
A spherical Fabry-Perot interferometer with adjustable mirror spacing is used
to produce interference fringes with frequency separation (c/2L)/N, N=2-15. The
conditions for observation of these fringes are derived from the consideration
of the eigenmodes of the cavity with high transverse indices.Comment: 11 pages, 7 figures, accepted to Siberian Journal of Physic
Relaxation of atomic polarization in paraffin-coated cesium vapor cells
The relaxation of atomic polarization in buffer-gas-free, paraffin-coated
cesium vapor cells is studied using a variation on Franzen's technique of
``relaxation in the dark'' [Franzen, Phys. Rev. {\bf 115}, 850 (1959)]. In the
present experiment, narrow-band, circularly polarized pump light, resonant with
the Cs D2 transition, orients atoms along a longitudinal magnetic field, and
time-dependent optical rotation of linearly polarized probe light is measured
to determine the relaxation rates of the atomic orientation of a particular
hyperfine level. The change in relaxation rates during light-induced atomic
desorption (LIAD) is studied. No significant change in the spin relaxation rate
during LIAD is found beyond that expected from the faster rate of spin-exchange
collisions due to the increase in Cs density.Comment: 14 pages, 14 figure
Tailorable dispersion in a four-wave mixing laser
We present experimental results demonstrating controllable dispersion in a ring laser by monitoring the lasing-frequency response to cavity-length variations. Pumping on an N-type level configuration in Rb-87, we tailor the intra- cavity dispersion slope by varying experimental parameters, such as pump-laser frequency, atomic density, and pump power. As a result, we can tune the pulling factor, i.e., the ratio of the laser frequency shift to the empty cavity frequency shift, of our laser by more than an order of magnitude. (C) 2017 Optical Society of Americ
Remote Detection Optical Magnetometry
Sensitive magnetometers have been applied in a wide range of research fields,
including geophysical exploration, bio-magnetic field detection, ultralow-field
nuclear magnetic resonance, etc. Commonly, magnetometers are directly placed at
the position where the magnetic field is to be measured. However, in some
situations, for example in near space or harsh environments, near nuclear
reactors or particle accelerators, it is hard to place a magnetometer directly
there. If the magnetic field can be detected remotely, i.e., via stand-off
detection, this problem can be solved. As optical magnetometers are based on
optical readout, they are naturally promising for stand-off detection. We
review various approaches to optical stand-off magnetometry proposed and
developed over the years, culminating in recent results on measuring magnetic
fields in the mesosphere using laser guide stars, magnetometry with
mirrorless-lasing readout, and proposals for satellite-assisted interrogation
of atmospheric sodium.Comment: 68 pages, 19 figure
Dynamic effects in nonlinear magneto-optics of atoms and molecules
A brief review is given of topics relating to dynamical processes arising in
nonlinear interactions between light and resonant systems (atoms or molecules)
in the presence of a magnetic field.Comment: 15 pages, 11 figure
Magnetometry with mesospheric sodium
Measurement of magnetic fields on the few 100-km length scale is significant for many geophysical applications including mapping of crustal magnetism and ocean circulation measurements, yet available techniques for such measurements are very expensive or of limited accuracy. We propose a method for remote detection of magnetic fields using the naturally occurring atomic sodium-rich layer in the mesosphere and existing high-power lasers developed for laser guide star applications. The proposed method offers a dramatic reduction in cost and opens the way to large-scale, parallel magnetic mapping and monitoring for atmospheric science, navigation, and geophysics. atomic physics | geomagnetism | optical pumping M easurements of geomagnetic fields are an important tool for peering into the Earth's interior, with measurements at differing spatial scales giving information about sources at corresponding depths. Mapping of fields on the few meter scale can locate buried ferromagnetic objects (e.g., unexploded ordnance or abandoned vessels containing toxic waste), whereas maps of magnetic fields on the kilometer scale are used to locate geological formations promising for mineral or oil extraction. On the largest scale, the Earth's dipole field gives information about the geodynamo at depths of several thousand kilometers. Magneticfield variations at intermediate length scales, in the range of several tens to several hundreds of kilometers likewise offer a window into important scientific phenomena, including the behavior of the outer mantle, the solar quiet dynamo in the ionosphere (1), and ionic currents as probes of ocean circulation (2), a major actor in models of climate change. To avoid contamination from local perturbations, measurements of such slowly varying components of the magnetic field must typically be made at a significant height above the Earth's surface (e.g., measurements of components with a spatial-variation scale of 100 km require an altitude of approximately 100 km) and with high sensitivity (on the order of 1 nT). Though magnetic mapping at high altitude has been realized with satellite-born magnetic sensors (3-5), the great expense of multisatellite missions places significant limitations on their deployment and use. Here, we introduce a high-sensitivity ground-based method of measuring magnetic fields from sources near Earth's surface with 100 km spatial resolution.* The method exploits the naturally occurring atomic sodium layer in the mesosphere and the significant technological infrastructure developed for astronomical laser guide stars (LGS). This method promises to enable creation of geomagnetic observatories and of regional or global sensor arrays for continuous mapping and monitoring of geomagnetic fields without interference from ground-based sources. Overview of Technique The measurement we envisage is a form of atomic magnetometry, adapted to the conditions of the mesosphere. The principle is to measure spin precession of sodium atoms by spin-polarizing them, allowing them to evolve coherently in the magnetic field, and determining the postevolution spin state. Spin polarization of mesospheric sodium is achieved by optical pumping, as proposed in the seminal paper on sodium LGS by Happer et al. (6). In the simplest realization, the pumping laser beam is circularly polarized and is launched from a telescope at an angle nearly perpendicular to the local magnetic field, as shown i
Modeling of pulsed laser guide stars for the Thirty Meter Telescope project
The Thirty Meter Telescope (TMT) has been designed to include an adaptive
optics system and associated laser guide star (LGS) facility to correct for the
image distortion due to Earth's atmospheric turbulence and achieve
diffraction-limited imaging. We have calculated the response of mesospheric
sodium atoms to a pulsed laser that has been proposed for use in the LGS
facility, including modeling of the atomic physics, the light-atom
interactions, and the effect of the geomagnetic field and atomic collisions.
This particular pulsed laser format is shown to provide comparable photon
return to a continuous-wave (cw) laser of the same average power; both the cw
and pulsed lasers have the potential to satisfy the TMT design requirements for
photon return flux.Comment: 16 pages, 20 figure
- …