Solitons in quadratic nonlinear photonic crystals.
We study solitons in one-dimensional quadratic nonlinear photonic crystals with modulation of both the linear and nonlinear susceptibilities. We derive averaged equations that include induced cubic nonlinearities, which can be defocusing, and we numerically find previously unknown soliton families. Because of these induced cubic terms, solitons still exist even when the effective quadratic nonlinearity vanishes and conventional theory predicts that there can be no soliton. We demonstrate that both bright and dark forms of these solitons can propagate stably.
Stable three-dimensional spinning optical solitons supported by competing quadratic and cubic nonlinearities.
We show that the quadratic interaction of fundamental and second harmonics in a bulk dispersive medium, combined with self-defocusing cubic nonlinearity, gives rise to completely localized spatiotemporal solitons (vortex tori) with vorticity s=1. There is no threshold necessary for the existence of these solitons. They are found to be stable if their energy exceeds a certain critical value, so that the stability domain occupies about 10% of the existence region of the solitons. On the contrary to spatial vortex solitons in the same model, the spatiotemporal ones with s=2 are never stable. These results might open the way for experimental observation of spinning three-dimensional solitons in optical media.
Modulation of the second-order nonlinear tensor components in multiple-quantum-well structures
In this paper, we present experimental results which demonstrate that quantum-well intermixing techniques can be used to modulate the magnitude of the second-order nonlinear coefficient /spl chi//sup (2)/. Impurity-free vacancy disordering with SiO/sub 2/ and Ga/sub 2/O/sub 3/ caps was used to modulate the position of the band edge and hence, the magnitude of /spl chi//sub eff//sup (2)/. Using a coupled quantum-well structure we were able to demonstrate modulation of the d/sub 33/ tensor components associated with the asymmetric structure and of the d/sub 14/ component associated with the bulk crystal structure.