Efficient gas-phase VUV frequency up-conversion

We describe a pulsed, atomic lead (Pb) vapor-based vacuum ultraviolet (VUV) frequency converter from 233 to 186 nm with near-unity photon conversion efficiency. This conversion is attained without phasematching and is accomplished by using electromagnetically induced transparency to drive a Raman transition to near-maximal coherence without loss or beam blow-up. Under these conditions, the linear and nonlinear polarizations of the generated 186-nm field are of the same order and complete conversion from the 233-nm field occurs within a single (nonphasematched) coherence length.