Optimization of sub-Doppler DAVLL on the rubidium D2 line

We discuss the physics of sub-Doppler DAVLL spectroscopy, which employs a pump beam with an axial magnetic field to induce dichroism in an atomic vapour. The dichroism is measured by a counterpropagating probe beam, while the pump generates sub-Doppler spectral features. The magnitude of the field is chosen to shift the frequency of the absorption features by an amount comparable to their linewidth. The reference signals obtained are ideal for laser frequency discriminant signals (laser 'locking' to the atomic transition) without frequency modulation. We discuss the sensitivity of the spectra to magnetic field, laser power and polarization purity, and suggest operating parameters for the 87 Rb F = 2 → F' = 3, 2 crossover transition which maximize the signal amplitude and gradient.