Phase-Matched High-Order Difference-Frequency Mixing in Plasmas

Abstract

The generation of coherent extreme ultraviolet radiation by phase-matched high-order difference-frequency mixing in plasmas is reported. The plasmas are produced by optical field ionization of atomic and molecular gases in an intense Ti:sapphire laser field. Phase matching for the high-order two-color $(\ensuremath{\omega},2\ensuremath{\omega})$ mixing process, $9\ensuremath{\omega}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}6(2\ensuremath{\omega})\ensuremath{-}3\ensuremath{\omega}$, is demonstrated for the first time.