Four-wave mixing in a non-degenerate four-level diamond configuration in the hyperfine Paschen-Back regime

We present an experimental study of seeded four-wave mixing (4WM) using a diamond excitation scheme (with states from the 5S_1/2, 5P_1/2, 5P_3/2 and 5D_3/2 terms) in a thermal vapour of ^87Rb atoms. We investigate the 4WM spectra under the application of a strong magnetic field (0.6 T). The Zeeman interaction is strong enough to realise the hyperfine Paschen-Back regime, which has the effect of separating the optical transitions by more than the Doppler width, thereby significantly simplifying the spectral features. We show that this facilitates a quantitative comparison, even in the regime of strong dressing, between experimental data and a simple theoretical model based only on four-level optical Bloch equations.