CC BY
5The 30th International Conference on Advanced Laser Technologies LM-O-18
ALT'23
Resonances of coherent population trapping in cells with pairs of alkali atoms, detected by the Ramsey method
G.V. Voloshin1, A.N. Litvinov1, K.A. Barantsev1, Ammosov A.P.1, A.S. Kuraptsev1, I.M.
Sokolov1
1- Peter the Great St.Petersburg Polytechnic University, 195251, St.Petersburg, Russia
gavriilvsh@gmail.com
The interaction of bichromatic laser radiation with the media of alkali atoms under certain conditions leads to the appearance of the effect of coherent population trapping [1, 2]. This phenomenon is resonant in nature with respect to the frequency difference between the two radiation components. The width of such resonances turns out to be much smaller than the width of the natural absorption line, which largely determines the possibility of using this phenomenon in such areas as quantum frequency standards, optical magnetometers, high-resolution spectroscopic devices, devices for recording and storing quantum information, and the development of lasers without inversion.
Recently, the method of detecting CPT resonances by means of pulsed pumping (the Ramsey method) has become widespread [3]. The width of the resonances, with this method, is determined solely by the temporal characteristics of the pulse sequences and can be made much smaller than the width of the CPT resonance detected by continuous radiation.
The cause of the CPT phenomenon is the destructive interference of two quantum excitation channels. For this reason, in the theoretical description of this phenomenon, simple three- and four-level models of atoms are often used [4, 5]. However, it is known that taking into account the "real" multilevel structure of alkali atoms in describing CPT excitation under certain conditions leads to significantly different qualitative results [6].
In this work, on the basis of the semiclassical theory of the interaction of light and matter using the density matrix method in the Wigner representation with respect to the translational degrees of freedom of atoms, a mathematical model of the interaction of pulsed bichromatic laser radiation with the resonant medium of alkali atoms is constructed, taking into account the non-zero temperature of the ensemble and the real (magnetic) structure of atomic levels . Based on this model, the contours of CPT resonances detected by two pulses separated in time by a dark pause are calculated. The calculation results are compared with experiments [7, 8]. The dependence of the shape of the resonances on various parameters of the atomic medium and laser pumping is analyzed.
This work was financially supported by the Theoretical Physics and Mathematics Advancement Foundation "BASIS" (Leader grant no. 21-1-1-36-1) and the Russian Science Foundation (grant no. 21-72-10004).
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