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.
Periodically switched nonlinear structures for frequency conversion: theory and experimental demonstration
In this paper, we report on the analytical study of a first-order quasi-phase-matched structure based on a periodically switched nonlinearity. The general average equations describing parametric wave interaction for this structure are obtained. The theoretical results are then used to analyze the special case of a device based on a semiconductor Al/sub x/Ga/sub 1-x/As waveguide for efficient frequency doubling in the mid-infrared to the far-infrared range. The necessary conditions to obtain an optimal configuration are discussed in both continuous wave and femtosecond-pulse regimes. Our analysis indicates that the conversion efficiency obtained should significantly exceed the efficiency obtained with a periodically poled lithium niobate crystal at long wavelengths. Finally, we include the preliminary results of the experimental demonstration of a waveguide device based on alternating domains of GaAs and Al/sub 0.4/Ga/sub 0.6/As.
Integrated two-beam antenna array featuring dual-circular polarization
A concept of an integrated antenna array featuring two independent beams and dual circular polarization has been described. The antenna array consists of two radiating elements which are excited at two orthogonally placed feeding ports with the use of four appropriately connected 3-dB/90° directional couplers. Therefore, such an array generates two symmetrically located beams having right-handed circular polarization (RHCP) and identical two beams having left-handed circular polarization (LHCP). The presented concept has been verified by the design and measurements of an antenna array operating at 2.4 GHz frequency range.