Phase matching techniques in the UV-EUV

The efficient upconversion of laser light into the UV and EUV regions of the spectrum has two major requirements: (1) the ability to generate photons in the required energy range through the nonlinear laser-atom interaction; and (2) the ability to coherently add, without absorption, the signal from a large number of radiating atoms. In past work using a hollow-waveguide geometry for frequency conversion, we demonstrated that it is possible to achieve high efficiency conversion into the UV and soft-X-ray regions. In this work, we show that this high efficiency allows us drive cascaded nonlinear upconversion processes from the visible to the VUV region of the spectrum with macroscopic conversion efficiencies. We also observe a type of quasi-phase matching in the deep-UV region of the spectrum. Finally, we use coherent control techniques to selectively enhance a single harmonic order, to generate transform-limited EUV pulses.