The cumulative resonance in atomic ground state induced by modulated light field

Piotr Put, Piotr Wcisło, Wojciech Gawlik +1 more

We report on investigations of nonlinear magneto-optical rotation (NMOR) in rubidium vapor subjected to a modulated magnetic field and continuous-wave (cw) laser-light illumination. By superimposing modulation and a static (dc) magnetic field, we demonstrate the appearance of resonances at both small and large (compared to the ground-state relaxation rate) values of the static field. Since in conventional NMOR there is no rotation at high fields, this suggests an existence of an alternative mechanism generating anisotropy in the considered case, which we identify as parametric resonance. The experiments are performed using light of small ellipticity, and rotation signals are significantly enhanced by combining atom-induced polarization rotation with a passive rotation induced with a wave plate. All the observations are supported with theoretical simulations. The density-matrix formalism and angular-momentum probability surfaces are used to provide an intuitive explanation of the observed signals.

V. G. Pokazan'ev, L. N. Novikov

Tadao Mochizuki, Kōichi Shimoda

A dynamic equation of atoms irradiated by a laser light in a magnetic field is applied to the light modulation experiment of atoms, whose excited states are not optically connected with the ground state. The resonance for the fluorescent light as a function of magnetic field is derived. The resonance curve for the fluorescent light from the lower level is found to be a superposition of resonance curves of two different widths. The broad component is a manifestation of the atomic coherence of the lower level. The narrow component is attributed to the atomic coherence of the upper level which is transferred to the lower level by spontaneous emission. The decay rate of the upper level is included in the expression of the resonance curve for the fluorescent light from the lower level.

G. A. Delone, Nikolai B. Delone, B. A. Zon +2 more

G. A. Delone, Nikolai B. Delone, B. A. Zon +2 more

Víctor M. Acosta, M. P. Ledbetter, Simon Rochester +7 more

Recent work investigating resonant nonlinear magneto-optical rotation (NMOR) related to long-lived $({\ensuremath{\tau}}_{\mathrm{rel}}\ensuremath{\sim}1\mathrm{s})$ ground-state atomic coherences has demonstrated potential magnetometric sensitivities exceeding ${10}^{\ensuremath{-}11}\phantom{\rule{0.3em}{0ex}}\mathrm{G}∕\sqrt{\mathrm{Hz}}$ for small $(\ensuremath{\lesssim}1\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{G}$) magnetic fields. In the present work, NMOR using frequency-modulated light (FM NMOR) is studied in the regime where the longitudinal magnetic field is in the geophysical range$(\ensuremath{\sim}500\mathrm{mG})$, of particular interest for many applications. In this regime a splitting of the FM NMOR resonance due to the nonlinear Zeeman effect is observed. At sufficiently high light intensities, there is also a splitting of the FM NMOR resonances due to ac Stark shifts induced by the optical field, as well as evidence of alignment-to-orientation conversion type processes. The consequences of these effects for FM-NMOR-based atomic magnetometry in the geophysical field range are considered.