Absolute acoustic band gap in coupled multilayer structures

We show theoretically that by combining two or more finite superlattices, i t is possible to realize an omnidirectional acoustic mirror that prevents p ropagation of acoustic waves over a wide range of frequencies. An appropria te choice of the elastic parameters in the superlattices enables us to prop ose a structure in which any incident wave launched from any type of substr ate ( or vacuum) falls inside a minigap of the coupled SLs and therefore un dergoes a total reflection.