Omnidirectional refractive devices for flexural waves based on graded phononic crystals

Abstract

Abstract. Different omnidirectional refractive devices for flexural waves in thin plates are proposed and numerically analyzed. Their realization is explained by means phononic crystal plates, where a previously developed homogenization theory is employed for the design of graded index refractive devices. These devices consist of a circular cluster of inclusions with properly designed gradient in their radius. With this approach, the Luneburg and Maxwell lenses and a family of beam splitters for flexural waves are proposed and analyzed. Results show that these devices work properly in a broadband frequency region, being therefore an efficient approach for the design of refractive devices specially interesting for nano-scale applications.

The SH0 wave manipulation in graded stubbed plates and its application to wave focusing and frequency separation

“…Since the SH0 wave generated at the point (−0.1 m, 0) spreads out rapidly, |uy| 2 decreases quickly, which makes the amplitude at the focusing point smaller than that at the generation position, which was also found in Ref. [39]. However, |uy| 2 at the focusing position is approximately five times larger than that at the corresponding point without the lens.…”

Three‐dimensional Luneburg lens at optical frequencies

“…The ability to focus a plane wave ideally for the 3D designed Luneburg lens is confirmed by comparing the experimental results with the simulated results. Note that a Luneburg lens is an ideal lens free from optical aberrations, whose focus size is limited by the wavelength of light, but it is not a perfect lens . The focus of a Luneburg lens is a finite‐sized spot, strictly speaking, a diffraction‐limited spot.…”

Gradient Index Devices for the Full Control of Elastic Waves in Plates

“…The control of the propagating characteristics of mechanical (acoustic and elastic) waves in linear media is a challenging problem with a wide variety of applications, since this control allows the design of acoustic or elastic lenses 1 2 3 4 5 6 , omnidirectional absorbers 7 8 9 , cloaking devices 10 11 12 or hyperlenses 13 . The propagation of mechanical waves can be tailored by means of inhomogeneous materials, as it is well known that in these media waves follow curved trajectories that can be properly designed if the position-dependent parameters of the medium are chosen according to specific laws.…”