Microwave phase-dependent optical absorption

It is known that a laser excited resonant Raman interaction causes atoms to be optically pumped into a nonabsorbing dressed state, the so-called trapped state. It is illustrated how a microwave field can modify this nonabsorbing state in a phase sensitive way to produce changes in the absorption of the optical Raman excitation fields. The three-level atomic system studied and the experimental setup used are described. With no microwave field, a Raman-Ramsey fringe line shape is observed. However, when microwave power corresponding to a π-pulse is present, the line shape exhibits oscillations produced by rapid scanning of the relative microwave and laser difference frequency phases. Large changes in optical absorption are produced by changing only the relative phase of the microwave field. Uses for this effect are suggested.