Abstract

We consider phase matching in generation of very short-wavelength coherent radiation by nonlinear frequency upconversion in plasma and suggest some ways to improve phase matching in high-order harmonic generation (HHG). We obtain the first to our knowledge simple analytical expressions for phase-matching factor in multiphoton mixing of an arbitrary order and demonstrate theoretically that high-order difference-frequency mixing in plasma could be, due to its potential for phase matching optimization, a more promising method of large-scale frequency upconversion than HHG.

© 1993 Optical Society of America