Negative refraction and energy funneling by hyperbolic materials: an experimental demonstration in acoustics.
This Letter reports the design, fabrication, and experimental characterization of hyperbolic materials showing negative refraction and energy funneling of airborne sound. Negative refraction is demonstrated using a stack of five holey Plexiglas plates where their thicknesses, layer separation, hole diameters, and lattice periodicity have been determined to show hyperbolic dispersion around 40 kHz. The resulting hyperbolic material shows a flat band profile in the equifrequency contour allowing the gathering of acoustic energy in a broad range of incident angles and its funneling through the material. Our demonstrations foresee interesting developments based on both phenomena. Acoustic imaging with subwavelength resolution and spot-size converters that harvest and squeeze sound waves irradiating from many directions into a collimated beam are just two possible applications among many.
Wave Phenomena Group, Department of Electronics Engineering, Universitat Politècnica de València, Camino de Vera s.n. (Edificio 7F), ES-46022 Valencia, Spain.
Victor M
VM
García-Chocano
Department of Photonics Engineering, Technical University of Denmark, Orsteds Plads, Building 343, DK-2800 Kongens Lyngby, Denmark.
Johan
J
Christensen
Wave Phenomena Group, Department of Electronics Engineering, Universitat Politècnica de València, Camino de Vera s.n. (Edificio 7F), ES-46022 Valencia, Spain.
José
J
Sánchez-Dehesa