EGAS41 - Swansea University

41 st EGAS CP 189 Gdańsk 2009
Quantitative spectroscopy of atoms in a strong magnetic field
based on an atomic vapor cell with L = λ
A. Papoyan 1,∗ , H. Hakhumyan 1 , A. Sargsyan 1 , D. Sarkisyan 1 , A. Atvars 2 , M. Auzinsh 2
1 Institute for Physical Research, NAS of Armenia, Ashtarak, 0203, Armenia
2 University of Latvia, Laser Centre, 19 Rainis Blvd., LV-1586 Riga, Latvia
∗ Corresponding author: papoyan@ipr.sci.am
Sub-Doppler nature of optical resonances forming in atomic spectra in alkali metal vapor
cells of nanometric thickness L [1] allows one to study peculiarities of magneto-optical
processes occurring in magnetic field for the case when L is of the order of (λ is a laser
resonant wavelength). A ”L = λ Zeeman technique” (λ–ZT) method has been developed
and implemented for investigation of the individual transitions between the Zeeman
sublevels of the hf structure of alkali atoms in a wide range of a B–field [2]. The λ–ZT
employs a nanometric cell with L = λ thickness and a cw diode laser radiation resonant
with D 1,2 lines of atomic 85 Rb, 87 Rb (λ = 794, 780 nm). At the laser intensity of a few
mW/cm 2 , narrow (∼10 MHz) velocity selective optical pumping/saturation (VSOP) resonances
appear in the transmission spectrum localized exactly at the atomic transitions.
The VSOP peaks are split into separate components in a B–field; the amplitudes (which
are proportional to transition probabilities) and frequency positions of the components
depend on the B–field. The preliminary studies have proved that λ–ZT is a very efficient
and convenient tool for determination of uniform and strongly non-uniform B–field
strength in the range of 0.1 mT ÷ 0.24 T. Among the advantages of λ–ZT is the possibility
to apply very strong magnetic fields using conventional strong permanent ring magnets
(PRM). In [2] the strong B–field was produced by two 30 mm PRMs, with d = 2 mm
holes to allow radiation to pass, placed on opposite sides of the nanocell oven and separated
by a distance varied between 35 and 50 mm. In spite of strong inhomogeneity of
the B–field (in our case it can reach ∼20 mT/mm), the variation of B inside the atomic
vapor column is a few µT, i.e., by several orders less than the applied B value because
of small thickness of the nanocell (∼800 nm).
Recently we have modified the nanocell oven design (typical operation temperature
is ∼100 o C), which allowed us reducing the distance between the PRMs down to 20 mm,
and thus increasing B up to ∼0.5 T. We prove that λ–ZT method is still perfectly valid
even for this high B value. In particular, a huge ∼7.5 GHz frequency shift of the VSOP
resonance formed at F g = 1 →F e = 2 transition of 87 Rb D 1 line from the B = 0 position in
the case of circular polarized excitation (σ + ) is observed when B ∼ 0.5 T, meanwhile for
σ − excitation the VSOP resonances amplitude strongly reduces with B. The comparison
of the experimental results with detailed calculations shows a good coincidence. Possible
applications of λ–ZT for diagnostics and mapping of large magnetic gradients and for
compact widely tunable frequency references will be addressed too.
Acknowledgment
A.P., D.S. acknowledge Armenian state co-funding of INTAS No.06-1000017-9001 Grant. A.A.,
M.A. acknowledge LNRP support in Material Sciences Grant No.1-23/50.
References
[1] D. Sarkisyan, D. Bloch, A. Papoyan, M. Ducloy, Optics Commun. 200, 201 (2001)
[2] A. Sargsyan, G. Hakhumyan, A. Papoyan, D. Sarkisyan, A. Atvars, M. Auzinsh, Appl.
Phys. Lett. 93, 021119 (2008)
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