Efficient generation of VUV radiation in coherently prepared mercury vapour - Martin Oberst

The enhancement of the generation of tunable vacuum ultra violet radiation at 125nm in atomic Hg vapor prepared in a state of maximum coherence is presented. The enhancement is accomplished by using a two-photon Stark chirped rapid adiabatic passage (SCRAP)-technique. This technique uses strong, off-resonant, pulsed electromagnetic fields in the infrared spectral region (1064nm) which generate dynamic Stark shifts in the nonlinear medium. These stark shifts are used to continuously tune the transition frequency of a two photon resonance in Hg which is addressed by a near resonant pump field at 313nm. Under certain conditions this leads to an adiabatic transfer process from the ground state to the 7s $^1S_0$ state of Hg which results in an complete population transfer to this state. As a consequence a maximum, transient coherence is prepared between the corresponding levels. This maximum coherence can be used to enhance the efficiency of the nonlinear four wave mixing process which generates the VUV radiation. The achieved enhancement is more than one order of magnitude with respect to conventional frequency conversion.