Experimental Evidence of the Existence of Bound States in the Continuum and Fano Resonances in Solid-Liquid Layered Media

Bound states in continuum (BICs) are resonances with zero width (infinite lifetime) without any leakage into the surrounding media. Their fascinating properties and potential applications have attracted a great deal of interest. In this paper, we give an analytical, numerical, experimental demonstration BICs simple acoustic structures based on either single solid layer or triple solid-liquid-solid inserted between two liquids. These modes intrinsic property structure (solid layer) free surfaces independent Two kinds discussed: (i) Fabry-Perot (FP) exist as consequence intersection local induced by intersect transmission zeros layers. (ii) Symmetry-protected (SP) occur when appear at normal incidence due to decoupling transverse from longitudinal that propagate solid-liquid multilayer When angle departs slightly BIC conditions, latter transform Fano characterized asymmetric line shape spectra. addition, show rise negative delay times therefore superluminal effect. The theoretical results obtained means Green's function method, whereas measurements carried out ultrasonic domain using plexiglass plates water. may important realize subsonic phenomena well filters sensors.