The method of transferring the frequency of an optically detected magnetic resonance both up and down by an arbitrary value is implemented in a single-beam optical pumping scheme by modulating the linearly polarized beam component. The possibility of observing the Hanle resonance in a magnetic field virtually zeroed upon transition to a rotating coordinate system is demonstrated. A model experiment was carried out, confirming the fundamental feasibility and effectiveness of the method. Keywords: Optically detectable magnetic resonance, optical resonance frequency transfer, Hanle effect, Bell-Bloom scheme, quantum magnetometer.
An experimental comparison of the methods for modulating the parameters of resonant transverse to the external magnetic field pumping radiation in a two-beam optical magnetometric sensor (so called Bell-Bloom scheme) is carried out, as well as a comparison of these methods with the standard method of radio-frequency excitation of magnetic resonance under conditions of strong laser pumping. It is shown that although the standard method allows one to achieve a greater suppression of the spin-exchange broadening of the magnetic resonance line by pumping light, the Bell-Bloom scheme has advantages that make it possible to obtain similar sensitivity values upon modulation of both the intensity and polarization of the pump light; at the same time, the Bell-Bloom scheme is potentially characterized by higher speed, which is essential for the problems of magnetoencephalography and ultra-low field magnetic resonance imaging.
An algorithm is proposed for the approximate solution of a purely nonlinear problem of the parameters of optically detected magnetic resonance in the ground state of alkali atoms in an optically dense medium under conditions of intense narrow-band optical pumping, which causes, first, bleaching of the atomic medium, and, second, partial suppression of spin-exchange broadening. The direct solution of the Liouville equation under these conditions is complicated by the fact that the relaxation time of each of the levels of the hyperfine and Zeeman structure of the ground state is determined by the populations of the remaining levels, which leads to the necessity of solving a self-consistent problem in a multilevel system, and, as a rule, requires the use of supercomputers. In this paper, approximations are proposed that make it possible to significantly simplify and speed up the calculation by orders of magnitude, and the results are compared with experimental data using the example of a two-beam Mx scheme of a magnetometric sensor
Specific types of atomic coherences between Zeeman sublevels can be generated and detected using a method based on nonlinear magneto-optical rotation with frequency-modulated light. Linearly polarized, frequency-modulated light is employed to selectively generate ground-state coherences between Zeeman sublevels for which $\mathrm{\ensuremath{\Delta}}m=2$ and $\mathrm{\ensuremath{\Delta}}m=4$ in
85Rb and
87Rb atoms, and additionally $\mathrm{\ensuremath{\Delta}}m=6$ in
85Rb. The atomic coherences are detected with a separate, unmodulated probe light beam. Separation of the pump and probe beams enables independent investigation of the processes of creation and detection of the atomic coherences. With the present technique the transfer of the Zeeman coherences, including high-order coherences, from excited to ground state by spontaneous emission has been observed.
In a previous paper, I have presented a general theory of the optical pumping of atoms by a polarized multimode-laser beam, in the presence of a magnetic field. Equations of motion, valid at arbitrary laser intensities for the density matrix of the atomic system, have been obtained. In this paper, these equations are exactly solved for a linearly $\ensuremath{\sigma}$-polarized laser and levels having small angular momenta. More precisely, I consider the laser transitions ${J}_{b}=1\ensuremath{\rightarrow}{J}_{a}=0$, ${J}_{b}=1\ensuremath{\rightarrow}{J}_{a}=1$, and ${J}_{b}=1\ensuremath{\rightarrow}{J}_{a}=2$. Two particular results are emphasized: (i) For $J=1\ensuremath{-}J=0$ and $J=1\ensuremath{-}J=1$ transitions and for the
J=2 level of a $J=1\ensuremath{-}J=2$ transition, the laser-induced Hanle effects keep a Lorentzian shape, independent of the laser intensity. For the $J=1\ensuremath{-}J=1$ transition, it is shown that the depolarizing relaxation processes play a leading part in the coupling induced by the laser between the transverse alignments of the two levels. On the other hand, the power broadenings of the Hanle effects are shown to be similar. For the
J=1 level of a $J=1\ensuremath{-}J=2$ transition, the Hanle-effect shape presents a departure from the Lorentzian one, owing to a coupling with the laser-induced hexadecapole moment in the
J=2 level. (ii) The populations of the levels exhibit a "zero-field saturation resonance" which is due to the coupling with the Zeeman coherences. These resonances, which reproduce the Hanle effects of the transition, can be observed on the $\ensuremath{\pi}$-polarized fluorescence from the levels. In general, these resonances appear as a saturation effect, i.e., they reduce the laser-induced fluorescence of the levels in zero magnetic field. However, for the ${J}_{b}=1\ensuremath{\rightarrow}{J}_{a}=2$ transition, the ${J}_{a}=2\ensuremath{\rightarrow}{J}_{f}=2 \ensuremath{\pi}$ fluorescence presents an anomalous behavior; the saturation resonance increases the zero-field laser-induced fluorescence. The theoretical study shows the prominent part played by the value of the
Jb=1 level lifetime in the interpretation of this anomaly. Other results, such as the laser-induced depolarization of the fluorescence, are also obtained. All the theoretical predictions have been experimentally checked and will be presented in forthcoming papers.