EGAS41 - Swansea University

41 st EGAS PR 5 Gdańsk 2009
Interferences in the Autler-Townes effect
Aigars Ekers 1 , N.N. Bezuglov 2 , K. Miculis 1 , T. Kirova 1 , B. Mahrov 1 , C. Andreeva 3 ,
R. Garcia-Fernandez 4 , I.I. Ryabtsev 5 , K. Bergmann 6 , J. Ulmanis 1 , M. Bruvelis 1 ,
M. Auzinsh 1 .
1 Laser Centre, University of Latvia, LV-1002 Riga, Latvia
2 Faculty of Physics, St. Petersburg State University, 198904 St. Petersburg, Russia
3 Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
4 Dept. of Physics, University of Mainz, D-55128 Mainz, Germany
5 Institute of Semiconductor Physics, 630090 Novosibirsk, Russia
6 Dept. of Physics, TU Kaiserslautern, D-67653 Kaiserslautern, Germany
The Autler-Townes effect is manifested when two levels are coupled by a strong coherent
radiation field. When one of those levels is coupled by a weak probe field to a third level,
the typical doublet can be observed in the probe excitation spectrum [1]. A number of
detailed studies in atoms [2] and molecules [3] exist. The present report is focused on
the possible applications of the Autler-Townes effect to population switching, and the
effects of resolved and unresolved hyperfine structure on the formation of laser-dressed
(adiabatic) states.
We consider a three-level system as in Fig. 1 coupled by two laser fields. If the
strong field P is coupled between levels g and e, then the excitation spectrum of level f
obtained by scanning the S field does not exhibit the expected doublet; instead, peculiar
broad lineshapes are observed [4]. These lineshapes can be explained by Ramsey-type
interference of the laser-dressed states. Moreover, such interference can be used in order
to achieve switching of the population of level f via variation of the S-field frequency
from a maximum to a minimum of the Remsey fringes.
Figure 1: Three-level linkage scheme in Na 2 .
New effects of hyperfine structure on the formation of laser-dressed states have also
been identified. We consider a scheme as in Fig. 1 but with strong coupling in the
second step and a weak probe in the first step, while each level has hyperfine sublevels.
Hyperfine magnetic sublevels are fully resolved in the Autler-Townes spectra if the number
of hyperfine levels in the two laser-coupled states is equal. If the number of hyperfine levels
is different, then the dark states are formed, which limits the hyperfine resolution.
References
[1] B.W. Shore, The Theory of Coherent Atomic Excitation (Wiley, New York, 1990)
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