Laser frequency stabilization to excited state transitions using electromagnetically induced transparency in a cascade system Available to Purchase

We demonstrate laser frequency stabilization to excited state transitions using cascade electromagnetically induced transparency. Using a room temperature Rb vapor cell as a reference, we stabilize a first diode laser to the $D2$ transition and a second laser to a transition from the intermediate $5P3/2$ state to a highly excited state with principal quantum number $n=19–70$⁠. A combined laser linewidth of $280±50kHz$ over a $100μs$ time period is achieved. This method may be applied generally to any cascade system and allows laser stabilization to an atomic reference in the absence of a direct absorption signal.