Nonlinear magneto-optical resonances atD1excitation ofRb85and

M. Auzinsh

¹

,

R. Ferber

²

,

F. Gahbauer

³

et al.

Abstract

Nonlinear magneto-optical resonances have been measured in an extremely thin cell (ETC) for the D1 transition of rubidium in an atomic vapor of natural isotopic composition. All hyperfine transitions of both isotopes have been studied for a wide range of laser power densities, laser detunings, and ETC wall separations. Dark resonances in the laser induced fluorescence (LIF) were observed as expected when the ground state total angular momentum Fg was greater than or equal to the excited state total angular momentum Fe. Unlike the case of ordinary cells, the width and contrast of dark resonances formed in the ETC dramatically depended on the detuning of the laser from the exact atomic transition. A theoretical model based on the optical Bloch equations was applied to calculate the shapes of the resonance curves. The model, which had been developed previously for ordinary vapor cells, averaged over the contributions from different atomic velocity groups, considered all neighboring hyperfine transitions, took into account the splitting and mixing of magnetic sublevels in an external magnetic field, and included a detailed treatment of the coherence properties of the laser radiation. Such a theoretical approach had successfully described nonlinear magneto-optical resonances in ordinary vapor cells. However, to describe the resonances in the ETC, key parameters such as the ground state relaxation rate, exited state relaxation rate, Doppler width, and Rabi frequency had to be modified significantly in accordance with the ETC's unique features. The level of agreement between the measured and calculated resonance curves achieved for the ETC was similar to what could be accomplished for ordinary cells. However, in the case of the ETC, it was necessary to fine-tune parameters such as the background and the Rabi frequency for different transitions, whereas for the ordinary cells, these parameters were identical for all transitions.

Magnetic Field Gradiometer with Sub-Micron Spatial Resolution Based on Caesium Vapour in an Extremely Thin Cell

“…For instance, nonlinear MORs have been studied experimentally and theoretically for D 1 excitation of atomic caesium, and the theoretical model [9] is successful for describing the resonances in detail [10]. Moreover, the theoretical model has proved itself by describing more complex systems with partially resolved hyperfine levels, such as the Rb D 1 and D 2 lines [11], [12], and it was in good agreement with experiments carried out in the ETC as well [13].…”

Relaxation mechanisms affecting magneto-optical resonances in an extremely thin cell: Experiment and theory for the cesiumD1line

“…In the case of the ETC even the lowest laser power used is noticeably higher than laser powers used in ordinary cell experiments, but, because of the strong relaxation by collisions with cell walls, noticeable deviations from experimental results start at only very high laser power densities. At such powers, by including the laser beam profile in the theoretical model, the agreement between theoretical calculations and experimental results could be greatly improved, especially in the description of the broader structure at larger magnetic field values (see [22]). …”

“…The basic approach of our theoretical description of magneto-optical signals has previously been described in [13] for ordinary vapor cells and expanded for the case of ETCs in [22]. In this section we describe how we extend the theoretical model to include a better description of the effects of transit relaxation and atom-wall collisions.…”

“…More sophisticated models were applied to describe experimentally measured magneto-optical signals obtained for the cesium D 2 [21] and rubidium D 1 [22] lines for atoms in ETCs, including all degenerate hyperfine levels of the excited-and ground-state manifolds. However, the proper treatment of collisions remained difficult and somewhat contradictory.…”

Evolution of dark state of an open atomic system in constant intensity laser field

“…Physical processes leading to line narrowing or broadening of coherent resonances were extensively studied under different experimental conditions, laser beam geometries, and cell dimensions [7][8][9][10][11][12]16,[25][26][27][28]. Figures 12(a) and 12(b) show experimental and theoretical results for the dependence Fig.…”