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Communication Dans Un Congrès Année : 2004

Measurements of APV magnetoelectric optical effects amplified by stimulated emission

Résumé

We detect atomic parity violation (APV), by using stimulated emission, in the form of a chiral optical gain of a cesium vapor on the 7S-6P3/2 transition, consecutive to linearly polarized 6S-7S excitation. The method relies on a pump-probe scheme in which the excited 7S state is populated, in zero B-field, by an intense, pulsed excitation beam, with a linear polarization Eex and a wave vector k parallel to the applied electric field E. The atoms are then probed by a second, collinear pulsed laser beam, tuned to resonance with the 7S-6P3/2 transition. The probe beam is amplified by stimulated emission and its linear polarization Epr undergoes a small change of direction, due to a linear dichroism arising from the presence of the pseudoscalar PV term (Eex.Epr)[ (Eex X Epr). E] in the gain, associated with a tilt theta^{pv} of the gain eigen-axes with respect to the plane of symmetry (Eex, k). The tilt of typically 1µrad, theta^{pv} = - Im E1pv/ beta.E, odd under E- reversal, is the relevant APV quantity. We measure it by balanced-mode two-channel polarimetry, with dedicated real-time calibration. We have demonstrated the validity of this detection method by performing a measurement of expected sign and magnitude with a 9% accuracy, now improved by more than a factor of two, thanks essentially to a dichroic polarization-tilt magnifier. Rotational symmetry around the common pump-probe axis is used to reduce systematic effects. Latest progress will be presented at the conference. Amplification of the left-right asymmetry by stimulated emission of radiation while the probe beam propagates through the excited vapor takes advantage of the large number of atoms excited along the pump-beam path. In the longitudinal El-field configuration currently exploited, this number is limited only by the total voltage sustainable by the Cs vapor. In order to overcome this limit, we consider, both theoretically and experimentally, the possibility of performing the measurements in transverse E-field pump-probe configuration, requiring a much lower voltage. We discuss the necessarily different nature of the observable and the magnetoelectric optical effects of a novel kind that occur. They condition modifications of the experimental configuration with, in particular, the application of a transverse magnetic field. We suggest a means of rotating the transverse direction of the fields so as to suppress systematic effects. With a long interaction length (typically 40cm), a precision reaching 0.1% in a quantum noise limited measurement can be expected, in this case limited only by the necessity of operating below the threshold of spontaneous superradiant emission of the excited medium. By approaching this limit, however, we could greatly amplify the asymmetry using triggered superradiance.

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Dates et versions

hal-00002781 , version 1 (07-09-2004)

Identifiants

  • HAL Id : hal-00002781 , version 1

Citer

Jocelyne Guéna, Michel Lintz, Marie-Anne Bouchiat. Measurements of APV magnetoelectric optical effects amplified by stimulated emission. ICAP 2004, 2004, Rio de Janeiro, Brazil. ⟨hal-00002781⟩
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