PHASE-MATCHED FREQUENCY-CONVERSION IN IONIZING ATOMIC GASES

We solve the one-dimensional wave equation for high-order mixing of th e type omega(h)=q omega(0) -l omega(c)(q much greater than l > = 1) us ing a Keldysh-type model to describe the high-field atomic nonlinear s usceptibility. When omega(c) is selected to give static phase matching , we show that the conversion efficiency of the mixed field can be inc reased by about an order of magnitude compared to non-phase-matched hi gh-order harmonic generation but that fundamental limitations are intr oduced by axial electron-density gradients.