Alexander, Tristram JSaltiel, Solomon MSukhorukov, AndreyKivshar, Yuri2015-12-130375-9601http://hdl.handle.net/1885/89414A concept of multistep cascading is applied to the problem of fourth-harmonic generation (FHG) in a single quadratic crystal, and a new model of parametric wave mixing is analyzed in detail. Important applications to the optical frequency division and efficient FHG as well as the realization of the double-phase-matching multistep cascading processes in engineered QPM structures with phase-reversal sequences are also suggested.Keywords: absorption; article; crystal; frequency analyzer; mathematical analysis; mathematical model; nonlinear system; optics200110.1016/S0375-9601(01)00106-22015-12-12