Effective Faraday interaction between light and nuclear spins of helium-3 in its ground state: a semiclassical study

We derive the semiclassical evolution equations for a system consisting of helium-3 atoms in the 2³S metastable state interacting with a light field far-detuned from the 2³S − 2³P transition, in the presence of metastability exchange collisions with ground state helium atoms and a static magnetic field. For two configurations, each corresponding to a particular choice of atom-light detuning in which the contribution of either the metastable level F = 1 / 2 or F = 3 / 2 is dominant, we derive a simple model of three coupled collective spins from which we can analytically extract an effective coupling constant between the collective nuclear spin and light. In these two configurations, we compare the predictions of our simplified model with the full model.