Propagation and interaction of extremely short electromagnetic pulses in quadratic-nonlinear medium

Propagation of extremely short unipolar pulses of electromagnetic waves was considered in framework of the anharmonic oscillator model. For quasi-harm onic waves, the model leads to the description of quadratic parametric proc esses, e.g., sum-frequency and difference-frequency mixings. Unipolar stead y state pulse was obtained by an analytical method. In numerical simulation s it was shown that these steady state pulses are stable under collisions. However, these pulses are not solitons in the strict sense. (C) 1999 Publis hed by Elsevier Science B.V. All rights reserved.