angles
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Let us summarize the requirements on the laser polarizations. In Sec. \[sec:g-states\] we showed that the cooling laser beam should be linearly polarized. If we are far from Raman resonance, its function, from the point of view of dark states, is merely to pump population into the metastable levels, where the repumper can then build up coherences (dark states) unless these are destabilized. Hence the effect of the angle between the magnetic field and the linear cooling laser polarization is negligible, typically only a few percent for the parameters considered here. On the other hand, near Raman resonance the number, position, and amplitude of the ground-metastable CPT resonances depend strongly on the polarization of both laser fields, but this is a regime we try to avoid.

The polarization angle of the repumper is crucial for the magnetic-field destabilization to work (see Fig. \[fig:RepumpAngle\]). It works only when the dark states are superpositions, i.e., when the repumper contains both $\sigma^+$ and $\sigma^-$. For all other polarizations ($\pi$, $\sigma^+$, $\sigma^-$, combination of $\pi$ and $\sigma^+$ *or* $\sigma^-$, but not both) there is at least one dark eigenstate into which optical pumping occurs.

![\[fig:RepumpAngle\](Color online) Scattering rate as a function of 