49 research outputs found
Role of different type of sub-systems in doubly driven Lambda-system in 87Rb
The well known Lambda-system using two ground state hyperfine levels, F=1 and
F=2 of 5S1/2 and one hyperfine level, F=2 of excited state of 5P3/2 of 87Rb has
been recently studied using two counter- propagating control lasers [1]. The
experiment shows conversion of electromagnetically induced transparency (EIT)
into electromagnetically induced absorption (EIA) because the doubly driven
Lambda-system forms various sub-systems. We here present detailed theoretical
study of the different possible sub-systems created by this configuration. We
also explore the possibility of tuning the strength of individual sub-systems
by changing the polarization of the control lasers
Conversion between electromagnetically induced transparency and absorption in a three-level lambda system
We show that it is possible to change from a {\it subnatural}
electromagnetically induced transparency (EIT) feature to a {\it subnatural}
electromagnetically induced absorption (EIA) feature in a (degenerate)
three-level system. The change is effected by turning on a second
control beam counter-propagating with respect to the first beam. We observe
this change in the line of Rb in a room-temperature vapor cell. The
observations are supported by density-matrix analysis of the complete sublevel
structure including the effect of Doppler averaging, but can be understood
qualitatively as arising due to the formation of -type systems with the two
control beams. Since many of the applications of EIT and EIA rely on the
anomalous dispersion near the resonances, this introduces a new ability to
control the sign of the dispersion.Comment: 6 pages, 7 figure
High-resolution hyperfine spectroscopy of excited states using electromagnetically-induced transparency
We use the phenomenon of electromagnetically-induced transparency in a
three-level atomic system for hyperfine spectroscopy of upper states that are
not directly coupled to the ground state. The three levels form a ladder
system: the probe laser couples the ground state to the lower excited state,
while the control laser couples the two upper states. As the frequency of the
control laser is scanned, the probe absorption shows transparency peaks
whenever the control laser is resonant with a hyperfine level of the upper
state. As an illustration of the technique, we measure hyperfine structure in
the states of Rb and Rb, and obtain an improvement of
more than an order of magnitude over previous values.Comment: 7 pages, 6 figure
Atomic fountain of laser-cooled Yb atoms for precision measurements
We demonstrate launching of laser-cooled Yb atoms in a cold atomic fountain.
Atoms in a collimated thermal beam are first cooled and captured in a
magneto-optic trap (MOT) operating on the strongly-allowed transition at 399~nm (blue line). They are then transferred to a MOT
on the weakly-allowed transition at 556~nm (green
line). Cold atoms from the green MOT are launched against gravity at a velocity
of around 2.5~m/s using a pair of green beams. We trap more than atoms
in the blue MOT and transfer up to 70\% into the green MOT. The temperature for
the odd isotope, Yb, is 1~mK in the blue MOT, and reduces by a
factor of 40 in the green MOT.Comment: 6 pages, 7 figure
Polarization-rotation resonances with subnatural widths using a control laser
We demonstrate extremely narrow resonances for polarization rotation in an
atomic vapor. The resonances are created using a strong control laser on the
same transition, which polarizes the atoms due to optical pumping among the
magnetic sublevels. As the power in the control laser is increased,
successively higher-order nested polarization rotation resonances are created,
with progressively narrower linewidths. We study these resonances in the
line of Rb in a room-temperature vapor cell, and demonstrate a width of for the third-order rotation. The explanation based on a simplified
V-type level structure is borne out by a density-matrix analysis of
the system. The dispersive lineshape and subnatural width of the resonance
lends itself naturally to applications such as laser locking to atomic
transitions and precision measurements.Comment: 5 pages, 6 figure