Efficient vacuum ultraviolet generation using electomagnetically induced transparency

The techniques of electromagnetically induced transparency (EIT) can be employed to create a nonlinear response at a given wavelength that is equal in magnitude to the linear response at that wavelength. Physically, this allows frequency converters wherein unity photon-to-photon conversion occurs within a single coherence length, i.e., in that distance that causes a n phase slip between the driving polarization and the generated field. These ideas were first implemented by Jain and coworkers´ to convert 425-nm radiation to 293-nm radiation with an energy conversion efficiency of 40%. We have extended that work to the generation of coherent radiation below 200nm, outside the transparency window of most nonlinear crystals. This was possible with moderate pump intensities without the need for phase matching