Structural Lens Based on Variable Thickness Structures

TL;DR

This paper introduces a novel variable thickness structural lens that achieves broadband triple focusing and beam splitting in elastic waves, with tunable focal points and directions, using a simple, miniature design inspired by optical principles.

Contribution

The study presents a new structural lens design based on variable thickness in a thin plate, enabling triple focusing and beam splitting for elastic waves with broadband capabilities.

Findings

Successfully achieved triple focusing and beam splitting in elastic waves.

Demonstrated tunability of focal points and beam directions by adjusting thickness profiles.

Validated the lens performance through analytical, numerical, and experimental methods.

Abstract

In this article, we report a lens design based on a concentric circular structure with continuous changing of thickness defined in a thin plate structure for focusing a plane wave into three spots (triple focusing) and for splitting elastic waves emanating from a point source into three collimated beams of different directions (three-beam splitting). Inspired by the principle of optical graded index triple focusing lens, the governing equations of the gradient refractive index profiles necessary for achieving such structural lens were obtained. The refractive index profiles were realized by using a lens design with two concentric circular areas of different thickness variation profiles defined in a thin plate. Analytical, numerical, and experimental studies were conducted to investigate the functionalities of the variable thickness structural lens. The results showed that the lens developed in this study were able to perform triple focusing and three-beam splitting with broadband property. Furthermore, the locations of focal points and directions of collimated beams can be engineered by changing the lens thickness profiles according to the governing equations. In addition, the proposed lens is miniature and simple design, which overcome the limitations of previous triple focusing and beam splitters.