Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-Jtransition

Abstract

A low-light-power theory of nonlinear magneto-optical rotation of frequency-modulated light resonant with a J = 1 → J ′ = 0 transition is presented. The theory is developed for a Doppler-free transition, and then modified to account for Doppler broadening and velocity mixing due to collisions. The results of the theory are shown to be in qualitative agreement with experimental data obtained for the rubidium D1 line.

Nonlinear magneto-optical rotation with frequency-modulated light in the geophysical field range

“…This numerical calculation extends our previous analytic calculation [23] to arbitrary light intensities and angular momenta using the method of Ref. [37].…”

“…Solid symbols represent the component in-phase with the light modulation, hollow symbols represent the component out-ofphase (quadrature) with the light modulation. At the low magnetic fields investigated in previous FM NMOR studies [18,23,31], a single, unsplit, dispersive (absorptive) feature was seen in the in-phase (quadrature) component. These data demonstrate that in the geophysical field range, the FM NMOR signals for 87 Rb take on a more complicated shape, the result of three separate resonances corresponding to the three ∆M F = 2 Zeeman coherences created in the F = 2 ground state (Fig.…”

“…Consequently, the optical properties of the medium are modulated at the quantum-beat frequency, leading to modulation of the angle of the light polarization. If the time-dependent optical rotation is measured at the first harmonic of the modulation frequency Ω m , ultra-narrow resonances are observed at near-zero magnetic fields, and at fields where the modulation frequency Ω m is a subharmonic of one of the quantum-beat frequencies of the system [18,23,31]. It should be noted that this technique yields a scalar magnetometer: the precession frequency is dependent only on the magnitude of the magnetic field and not its direction.…”

“…Our approach to atomic magnetometry [16,17,18,23] has focused on the use of nonlinear magneto-optical rotation (NMOR) [24] related to long-lived (τ rel ∼ 1 s) ground-state atomic coherences in alkali vapors. The long coherence times are obtained by containing roomtemperature (T ∼ 20…”

“…In order to translate the magnetometric sensitivity of NMOR in paraffin-coated cells to magnetic fields where Ω L ≫ γ rel , the technique of NMOR with frequencymodulated light (FM NMOR) was developed [18,23], with estimated sensitivities better than 10 −11 G/ √ Hz. Linearly polarized, frequency-modulated laser light, propagating in the direction of the magnetic field, is used for optical pumping and probing of the ground state atomic polarization.…”