Modulation of the Absorption of Resonance Emission in the Case of Excitation by Modulated Light

Olivier Émile, Fabien Bretenaker, A. Le Floch

The existence of a novel resonance in the modulation of the fluorescence light emitted by an atom or a molecule when coherently excited by a rapidly rotating linearly polarized light beam is predicted. Such resonances are experimentally observed due to a transfer of coherence from light to atoms or molecules, via either stimulated emission or absorption of light, without having to shift the positions of the levels by an external perturbation. These resonances directly permit the measurement of energy level lifetimes, even in the case where usual magnetic resonance methods would require the use of large magnetic fields.

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

Azriel Z. Genack, P. M. Mitra, Axel Schenzle

The response of emission in I2 vapor to intensity modulated light at radial frequency ω is measured and described in terms of the lifetime of the excited state, T1, the rate of phase interrupting collisions γ, and the inhomogeneously broadened absorption line. When the laser is tuned to resonance, the variation of amplitude of the modulated emission with ω corresponds to a single exponential decay with lifetime T1. Off resonance, the modulation is described as the sum of the above ‘‘delayed’’ component and a ‘‘prompt’’ in‐phase component which is independent of modulation frequency. The ratio of the delayed to prompt component for off resonant excitation is shown to be 2γT1. This relation is used to determine the rate of phase interrupting collisions in I2 vapor.

R. I. Sokolovskiǐ

Evgenii B. Aleksandrov, O. V. Konstantinov, V. I. Perel

Alan Corney, George William Series

When resonance fluorescence is excited in atoms whose excited states have Zeeman or hyperfine structure, it is to be expected that the character of the fluorescent light will be affected if the intensity of the exiciting light is modulated or pulsed. An earlier theory of resonance fluorescence is developed to take account of such variations of the intensity of the exciting light. Resonance effects are predicted if the light is modulated at a frequency which coincides with a characteristic frequency of the atoms. A particular case, which has been studied experimentally, is worked out in detail. If the exciting light is pulsed, the prediction is that the fluorescent light will be modulated, in addition to being damped at the ordinary rate for spontaneous emission.