Multistep cascading and fourth-harmonic generation

A concept of multistep cascading is applied to the problem of fourth-harmon ic generation (FHG) in a single quadratic crystal, and a new model of param etric wave mixing is analyzed in detail. Important applications to the opti cal frequency division and efficient FHG as well as the realization of the double-phase-matching multistep cascading processes in engineered QPM struc tures with phase-reversal sequences are also suggested. (C) 2001 Elsevier S cience B.V. All rights reserved.