| Current state of the art solid state nonlinear optics and laser technology can provide laser wavelengths throughout most of the visible and near infrared portion of the electomagnetic spectrum. Nonlinear crystals, however, are not transparent in the vacuum ultraviolet (VUV) or the far infrared (IR), and laser frequencies in these areas of the spectrum are still largely unavailable. We have developed a technique using four-wave-mixing (FWM) in atomic and molecular gases that is highly efficient, requires relatively low pump intensities and can generate fields in the VUV and far IR without loss. Specifically, we demonstrate 100% conversion efficiency from 233 nm to 186 nm in the VUV, in atomic lead vapor. This conversion is attained without the need for external phasematching agents, at power densities (4–8 MW/cm2) significantly lower than those typically used in FWM experiments. These high conversion efficiencies are accomplished by driving a Raman transition to near-maximal coherence. Under these conditions, the linear and nonlinear polarizations of the generated field are of the same order and complete conversion occurs within a single (non-phasematched) coherence length. |
