Faraday Effect in Rubidium Atomic Layers Thinner than 100 nm
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Faraday Effect in Rubidium Atomic Layers Thinner than 100 nm A. Sargsyana,*, A. Amiryana,b, and D. Sarkisyana,** a
Institute for Physical Research, National Academy of Sciences of Armenia, Ashtarak, 0203 Armenia b Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS, Université Bourgogne Franche-Comte, Dijon, 6303 France *e-mail: [email protected] **e-mail: [email protected] Received June 30, 2018; revised June 30, 2018; accepted September 13, 2018
Abstract—The interaction of rubidium atoms with sapphire cell windows at an interwindow distance L = 40– 100 nm is studied. For studies, we used the Faraday rotation (FR) effect (rotation of the plane of radiation polarization in a magnetic field) in a thin rubidium atom vapor column for D1, 2 lines. When L decreases from 100 to 40 nm, a red shift of the FR signal frequency is detected: it increases from 10 to 250 MHz, and the broadening of the low-frequency wing increases to ~1 GHz. The atomic transition Fg = 3 → Fe = 2 for the D1 line of 85Rb is shown to be convenient for such investigations, since it can be spectrally separated from other strongly broadened atomic transitions. Coefficients C3, which characterize the atom–surface interaction for the D1 and D2 lines of Rb, are determined. An additional red frequency shift takes place at a nanocell thickness L < 100 nm when the Rb atom density increases, and this shift is absent at large L. A practical application of an FR signal for measuring strong magnetic fields of several kilogausses is described. DOI: 10.1134/S1063776119020249
1. INTRODUCTION The simplest example of the van der Waals (VW) interaction (which still attracts attention of researchers) between two bodies is the interaction of a single atom located at a small distance (≤100 nm) from a dielectric surface [1]. The authors of [2–5] used selective reflection (SR) of laser radiation from thin alkali metal atomic layers. Laser radiation was normal to a window and SR radiation propagated in the opposite direction. SR is formed by a vapor column of alkali metal atoms of thickness L ≈ λ/2π, where λ is the laser wavelength with the frequency that is resonant to an atomic transition. Radiation with a wavelength λ = 895 nm, the frequency of which is resonant to the D1 line of Cs, was used in [1–3]. A small red frequency shift (several megahertz) of SR radiation was detected at a relatively small thickness (L ≈ 140 nm) because of the VW interaction. A large red frequency shift of several gigahertz was detected in [6]. A red frequency shift was also detected in the absorption and fluorescence spectra of Cs and Rb atoms in nanocells [7, 8]. As was shown in [9], the existence of a surface polariton at a wavelength of about 12 μm in a sapphire substrate– window (cell filled with Cs atoms) can be revealed by SR at a certain configuration of atomic levels. The authors of [9] used radiation of two lasers, and a sur-
face polariton manifested itself as a blue frequency shift at the 6P1/2–6D5/2 transition (λ = 876 nm). In [10], a semitransparent me
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