Search

We present an experimental scheme performing scalar magnetometry based on the fitting of Rb $ {{\rm D}_2} $D_2 line spectra recorded by derivative selective reflection spectroscopy from an optical nanometric-thick cell. To demonstrate its efficiency, the magnetometer is used to measure the inhomogeneous magnetic field produced by a permanent neodymium––iron–boron alloy ring magnet at different distances. The computational tasks are realized by relatively cheap electronic components: an Arduino Due board for external control of the laser and acquisition of spectra, and a Raspberry Pi computer for the fitting. The coefficient of variation of the measurements remains under 5% in the magnetic field range of 40–200 mT, limited only by the size of the oven and translation stage used in our experiment. The proposed scheme is expected to operate with high measurement precision also for stronger magnetic fields ($ {\gt} {500}\;{\rm mT}$>500mT) in the hyperfine Paschen–Back regime, where the evolution of atomic transitions can be calculated with high accuracy.

We have studied the peculiarities of selective reflection from an Rb vapor cell with a thickness L<70  nm, which is smaller than the length scale of evanescent fields λ/2π and more than an order of magnitude smaller than the optical wavelength. A 240 MHz redshift due to the atom-surface interaction is observed for a cell thickness of L=40  nm. In addition, complete frequency-resolved hyperfine Paschen–Back splitting of atomic transitions to four components for Rb87 and six components for Rb87 is recorded in a strong magnetic field (B>2  kG).

Decoupling of total electronic and nuclear spin moments of Cs atoms in an external magnetic field for the case of atomic D_1 line, leading to onset of the hyperfine Paschen–Back (HPB) regime, is studied theoretically and experimentally. Selective reflection (SR) of laser radiation from an interface of dielectric window and atomic vapor confined in a nanocell with 300 nm gap thickness is implemented for the experimental studies. The real-time derivative of SR signal with a frequency position coinciding with atomic transitions is used in the measurements, providing ∼40  MHz spectral resolution and linearity of the signal response with respect to the transition probability. The behavior of 28 individual Zeeman transitions in a wide range of longitudinal magnetic field (0–6 kG) is tracked under the excitation of Cs vapor by a low-intensity σ^+-polarized cw laser radiation. For B≥6  kG, only eight transitions with nearly equal probabilities and the same frequency slope remain in the spectrum, which is a manifestation of the HPB regime. The obtained experimental results are in very good agreement with the numerical modeling. A small divergence of the SR signal as well as subwavelength thickness and sub-Doppler spectral linewidth inherent to nanocell make it possible for the employed technique to be used for distant remote sensing of a magnetic field with high spatial and B-field resolution.

The saturation behavior of absorption and fluorescence spectra on the D_2 line of Cs is presented, demonstrating a significant difference between open and closed transitions. Cs vapor is confined in an extremely thin cell (ETC) with widely tunable thickness L=(0.5-3)λ, where λ is the light wavelength. In the saturation regime, the closed transition demonstrates enhanced absorption in a narrow spectral interval due to the Dicke effect, while the open one demonstrates only a velocity-selective dip in the absorption. The fluorescence of open transitions shows reduced fluorescence dips, enhancing their contrast with ETC thickness. The closed transition exhibits only a small plateau around the optical transition center. Applying two-level theoretical modeling based on optical Bloch equations, a qualitative agreement with experimental observations is achieved. The rate of contrast enhancement with cell thickness is larger for the theoretical than for the experimental dips. In addition, for the closed transition a tiny peak in the fluorescence is theoretically predicted, with the first experimental confirmation presented. The sub-Doppler spectra of vapor layers with a thickness of several light wavelengths show potential for realization of precise frequency references and photonics sensors.

N-type resonances excited in rubidium atoms confined in micrometric-thin cells with variable thickness from 1 μm to 2 mm are studied experimentally for the cases of a pure Rb atomic vapor and of a vapor with neon buffer gas. Good contrast and narrow linewidth were obtained for thicknesses as low as 30 μm. The higher amplitude and sharper profile of N-type resonances in the case of a buffered cell was exploited to study the splitting of the Rb85D_1N-resonance in a magnetic field of up to 2200 G. The results are fully consistent with the theory. The mechanism responsible for forming N-resonances is discussed. Possible applications are addressed.

We demonstrate electromagnetically induced transparency in a four-level cascade system where the upper level is a Rydberg state. The observed spectral features are sub-Doppler and can be enhanced due to the compensation of Doppler shifts with AC Stark shifts. A theoretical description of the system is developed that agrees well with the experimental results, and an expression for the optimum parameters is derived.

A simple and efficient scheme based on a one-dimensional nanometric-thin cell filled with Rb and strong permanent ring magnets allows direct observation of the hyperfine Paschen–Back regime on the D_1 line in the 0.5–0.7 T magnetic field. Experimental results are perfectly consistent with the theory. In particular, with σ^+ laser excitation, the slopes of the B-field dependence of frequency shifts for all 10 individual transitions of ^85,87Rb are the same and equal to 18.6??MHz/mT. Possible applications for magnetometry with submicron spatial resolution and tunable atomic frequency references are discussed.

In a previous Letter [Opt. Lett. 37, 3858 (2012)], three equations were misrepresented. They are corrected here.