Dual-functional dielectric metasurface doublets.

Multi-functional metasurface devices are of great importance for miniaturization and integration. Here we propose a novel approach to design dual-functional dielectric metasurface doublets based on the principle of Pancharatnam-Berry phase. The functionalities for the two operating wavelengths can be independently designed by adjusting the orientation angle of the nanofins in the upper layer and that in the lower layer, respectively. The functionality can be switched by simply changing the incident wavelength. The simulated results of the examples demonstrate that the designed dual-functional doublet works well as expected.

Optical solitons, self-focusing, and wave collapse in a space-fractional Schrödinger equation with a Kerr-type nonlinearity.

We investigate the nonlinear dynamics of (1+1)-dimensional optical beam in the system described by the space-fractional Schrödinger equation with the Kerr nonlinearity. Using the variational method, the analytical soliton solutions are obtained for different values of the fractional Lévy index α. All solitons are demonstrated to be stable for 1<α≤2. However, when α=1, the beam undergoes a catastrophic collapse (blow-up) like its counterpart in the (1+2)-dimensional system at α=2. The collapse distance is analytically obtained and a physical explanation for the collapse is given.

Observation of surface dark solitons in nonlocal nonlinear media.

We investigated surface dark solitons (SDSs) at the interface between a self-defocusing nonlocal nonlinear medium and a linear medium, both theoretically and experimentally. We demonstrate that fundamental and higher-order SDSs can exist when the linear refractive index of the self-defocusing medium is much greater than that of the linear medium. The fundamental and second-order solitons are observed at the interface between air and a weakly absorbing liquid.

Influence of the higher-orders of diffraction on the pattern evolution for tightly focused beams.

The mechanism of the nonparaxial propagation for tightly focused beams is investigated in the view of the influence of the higher-orders of diffraction (HOD). The HOD induce novel propagation characteristics which are crucially different from those predicted by the traditional paraxial theory. Based on the management of HOD, we propose an approach on controlling the intensity pattern of the focus to satisfy the application requirements.

Relation between surface solitons and bulk solitons in nonlocal nonlinear media.

We find that a surface soliton in nonlocal nonlinear media can be regarded as a half of a bulk soliton with an antisymmetric amplitude distribution. The analytical solutions for surface solitons and breathers in strongly nonlocal media are obtained, and the critical power and breather period are gotten analytically and confirmed by numerical simulations. In addition, the oscillating propagation of nonlocal surface solitons launched away from the stationary position is considered as interaction between the soliton and its out-of-phase image beam. Its trajectory and oscillating period obtained by our model are in good agreement with the numerical simulations.

Phase velocity nonuniformity-resulted beam patterns in difference frequency generation.

The evolution of the difference frequency generation between a planar pump wave and a focused signal wave has been numerically investigated in this paper. We show that, at the difference frequency wave, various beam patterns such as ring and moon-like, are resulted due to the nonuniform distribution of phase velocity in the focused signal wave. The subluminal and superluminal regions can be identified by the intersection of two generated beam profiles that correspond to a pair of phase-mismatches with equal value but opposite signs.