Modulation-free pump-probe spectroscopy of strontium atoms

We have performed polarization spectroscopy on the 5s^{2 1}S₀ →5s5p¹P₁ transition of atomic strontium. The signal is generated by saturation effects, rather than optical pumping, as the ground state is non-degenerate. This technique generated a dispersion-type lineshape suitable for laser stabilization, without the need for frequency modulation. The dependence of the amplitude and gradient on intensity and magnetic field were also investigated, and compared to a related technique based on the circular dichroism induced by a magnetic field.