Figure 2: Knight field determination and tuning.

(a) X⁺ Overhauser shift as a function of the applied field B_z. Circles (squares) for σ⁻(σ⁺) laser polarization, triangles for elliptically polarized laser excitation. The magnetic field B_z, for which this dip occurs, is a measure of the Knight field amplitude. Error bars are given by spectral precision. (b) Knight field amplitudes extracted by fitting Gaussians to data in a for three typical dots (X⁺ transitions for QDs five and 6B, X⁺ (solid squares) and X⁻ (hollow diamond) transitions for QD B), demonstrating Knight field tuning. The data show a roughly linear dependence as B_e∝‹S›∝(−/2), typical error bars due to precision of fitting procedure are indicated.