Experimental study of power broadening in a two-level atom

Two frequency-stabilized cw dye lasers and an atomic beam were used to prepare sodium atoms in the aligned $F=2\mathrm{}$, $M_F=2\mathrm{}$ ground state, and to study power broadening in the transition from this ground state to the $3P_{\frac{3}{2}}$ $F=3\mathrm{}$, $M_F=3\mathrm{}$ excited state. This system is, to extremely good accuracy, a two-level atom. The line shape was determined as a function of the incident field strength and found to be accurately a Lorentzian over a large range of incident field strengths. The power broadening and saturation at resonance of the two-level system also agree with theory.