In this volume, six review articles which cover a broad range of topics of current interest in modern optics are included.

The first article by S. Saltiel, A.A. Sukhorukov and Y.S. Kivshar presents an overview of various types of parametric interactions in nonlinear optics which are associated with simultaneous phase-matching of several optical processes in quadratic non-linear media, the so-called multi-step parametric interactions.
The second article by H.E. Tureci, H.G.L. Schwefel, Ph. Jacquod and A.D. Stone reviews the progress that has been made in recent years in the...