Resonant parametric amplification in four-level systems

Summary form only given. Resonant four-wave mixing with continuous laser fields has recently gained new interest, because of quantum interference effects that allow to manipulate and control the properties of the nonlinear medium. In this contribution we report on new experimental and theoretical investigations of four-wave mixing and parametric amplification in a resonantly driven double-A scheme as shown. As a nonlinear medium Na/sub 2/-molecules produced in a sodium heat pipe at a typical operation temperature of 720 K are used. In this scheme Raman gain on the 2-3 transition plays an important role and can result in exponential growth of the generated signal intensity at /spl lambda//sub 4/=480 nm in spite of absorption on the 4-1 transition (due to the "gain transfer"). This allows to achieve very high conversion efficiencies into the signal field.