EGAS41 - Swansea University

41 st EGAS CP 99 Gdańsk 2009
High resolution laser spectroscopy of Cs vapor layers with
thickness variation around the light wavelength
K. Vaseva 1,∗ , S. Cartaleva 1 , S. Saltiel 2 , D. Sarkisyan 3 , D. Slavov 1 , P. Todorov 1
1 Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Shosse bld, 1784
Sofia, Bulgaria
2 Sofia University, Faculty of Physics, 5 J. Bourchier boulevard, 1164 Sofia, Bulgaria
3 Institute for Physical Research, National Academy of sciences of Armenia, Ashtarak-2,
Armenia
∗ Corresponding author: kapkavaseva@mail.bg,
The high resolution spectroscopy of thin vapor layers has been made possible through
the development of unique optical cell, the so called Extremely Thin Cells (ETC) with
thickness around one micron [1].
In the presented work we examined, both theoretically and experimentally, the sub-
Doppler resonances in the transmission and fluorescence spectra on the D 2 line of Cs
atomic vapor layers with thickness L = mλ (where m = 0.5, 1, 1.5, 2, 2.5, 3), irradiated
by tunable single-frequency diode laser light. For low laser intensities and m = 0.5, 1.5,
2.5, in the transmission spectra the coherent Dicke narrowing is observed [2, 3], while for
m = 1, 2, 3 the hyperfine structure is not resolved. In the last case, under high-intensity
irradiation narrow dips of reduced absorption are observed, related to velocity selective
optical pumping and saturation. For m = 1.5, 2.5 and for the closed transition only, a
small absorption peak appears superimposed on the velocity selective deep. The difference
between the open and closed transition behaviour can be related to the fact that
for the open transitions the slowest atoms are effectively transferred to the ground-state
level non-interacting with the light. Thus, they are lost for the absorption and can not
participate in the formation of the coherent signal responsible for the Dicke narrowing.
The ETC fluorescence profiles are intrinsically narrower than the absorption profiles [4].
Nevertheless, well pronounced narrow saturation dips appear in the fluorescence profiles,
for all open transitions. The dip amplitude increases with the ETC thickness. In the case
of closed transition, non-suffering population loss a small feature in the fluorescence profile
is observed [5]. The utilized theoretical model is based on the Optical Bloch Equations for
two-level system (closed and open) [4]. For both absorption and fluorescence theoretical
profiles, we have obtained a qualitative agreement with the experimental observations.
Presented results contribute to the further advancement in fundamental studies of saturation
and optical pumping in extremely thin vapor layers.
Acknowledgment
Authors are grateful for the support by Bulgarian Fund of Scientific research (grant: DO-02-
108/22.05.2009) and Indian-Bulgarian bilateral collaboration (project: BIn-2/07).
References
[1] D. Sarkisyan, D. Bloch, A. Papoyan, M. Ducloy, Opt. Commun. 200, 201 (2001)
[2] S. Briaudeau, D. Bloch, M. Ducloy, Europhys. Lett. 35, 337-342 (1996)
[3] D. Sarkisyan, T. Varzhapetyan, A. Sarkisyan, Yu. Malakyan, A. Papoyan, A. Lezama,
D. Bloch, M. Ducloy, Phys. Rev. A 69, 065802 (2004)
[4] C. Andreeva, S. Cartaleva, L. Petrov, S.M. Saltiel, D. Sarkisyan, T. Varzhapetyan, D.
Bloch, M. Ducloy, Phys. Rev. A 76, 013837 (2007)
[5] P. Todorov, K. Vaseva, S. Cartaleva, D. Slavov, I. Maurin, S. Saltiel, Proc. SPIE, vol.
7027, 70270R (2008)
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