Design Of Subwavelength Structures Research Articles

Subwavelength Structures on Fused Silica for High-Power Laser Antireflection Applications

In the field of high-power lasers, subwavelength structures with both high transmittance and high laser damage resistance are required. However, in most of the studies, structural design tends to focus on optical properties. In this study, we research transmittance and surface electric field together. The surface light intensity, as an important damage factor, is investigated and quantitatively calculated using finite element method. Our results show that the surface light intensity has asymmetry on the front and rear surfaces, and is greatly regulated by the structural parameters. Based on this study, the subwavelength structures are designed which have both high transmittance and high laser damage resistance. Our research provides a new perspective to design of subwavelength structures, which is important for high-power laser antireflection applications.

Enhanced energy dissipation with nonlinear snapping acoustic metamaterial inclusions

Through the design of subwavelength structures, nonlinear acoustic metamaterials can be engineered to exhibit regimes of positive and negative incremental stiffness. Negative incremental stiffness leads to large, rapid deformation, commonly called snapping, between local stable configurations. When perturbed by a small external pressure, snapping elements can be exploited to enhance energy absorption of acoustic waves. The present research focuses on a low volume fraction of snapping inclusions, dispersed within a nearly incompressible viscoelastic matrix to create a multiscale nonlinear material. The forced dynamic response of the heterogeneous material is modeled using a generalized Rayleigh-Plesset equation, which couples the dynamic behavior at the micro- and macroscale. We investigate the nonlinear dynamic behavior of the heterogeneous medium for small harmonic perturbations about several pre-strains of the snapping inclusions to demonstrate the influence of the microscale dynamic response on the macroscale response. Of primary interest are energy dissipation capabilities and characteristic acoustic impedance, which change with inclusion pre-strain. The behavior is also compared to heterogeneous media created from conventional inclusions, such as air voids and steel inclusions, to demonstrate the wide range of material behavior obtained using snapping inclusions. [This work was supported by the Office of Naval Research.]