A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low-cost, high-efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging.

We demonstrate both theoretically and experimentally the physical mechanism that underlies extraordinary acoustic transmission and collimation of sound through a one-dimensional decorated plate. A microscopic theory considers the total field as the sum of the scattered waves by every periodically aligned groove on the plate, which divides the total field into far-field radiative cylindrical waves and acoustic surface evanescent waves (ASEWs). Different from the well-known acoustic surface waves like Rayleigh waves and Lamb waves, ASEW is closely analogous to a surface plasmon polariton in the optical case. By mapping the total field, the experiments well confirm the theoretical calculations with ASEWs excited. The establishment of the concept of ASEW provides a new route for the integration of subwavelength acoustic devices with a structured solid surface.

Nonlinear ultrasonic Lamb waves are popular to characterize the nonlinearity of materials. However, the widely used nonlinear Lamb mode suffers from two associated complications: inherent dispersive and multimode natures. To overcome these, the symmetric Lamb mode (S0) at low frequency region is explored. At the low frequency region, the S0 mode is little dispersive and easy to generate. However, the secondary mode still exists, and increases linearly for significant distance. Numerical simulations and experiments are used to validate the nonlinear features and therefore demonstrate an easy alternative for nonlinear Lamb wave applications.

In this work, we demonstrate the broadband scattering of light waves incident on coupled silicon nanocylinders. First, it is shown that both electric and magnetic resonances are observed in a single silicon nanocylinder. By using two silicon nanocylinders, we next construct a silicon nanodimer. Thereafter, the original electric and magnetic resonances of the single nanocylinder shift and form hybrid resonant modes in the dimer; meanwhile, a new magnetic resonant mode emerges at a longer wavelength. Consequently, the silicon nanodimer exhibits a broadband scattering response that originates from optically magnetic interactions between dimeric silicon nanocylinders. Furthermore, the scattering bandwidth further increases upon using a silicon nanotrimer. This broadband optical response in silicon nanocylinders is demonstrated via their scattering spectra, and the magnetic interaction is verified by examining the spatial distributions of electromagnetic fields and the retrieved permittivity and permeability of the nanocylinders system. This theoretical finding may provide an approach to realize silicon-based broadband nanoantennas and nanosensors.