Design of a Superlattice-Based Phonon Optics Device
Phonon optics devices such as frequency-selective phonon filters and reflectors based on thin-film superlattice structures were suggested by Narayanamurti several years ago . Here, we propose a new type of phonon optics device. The system we consider has a double barrier structure for phonons consisting of a bulk material sandwiched between periodic superlattices . Schematic frequency-band diagram for this system is shown in Fig. 1. In this figure, the hatched regions indicate the frequency gaps of superlatt ices. The phonons within these frequency gaps cannot be transmitted through the system. In other words, the superlattices act as barriers for phonon; with frequencies between w L and w H . Thus, we can regard the system shown in Fig. 1 as a double barrier system for phonons in the forbidden gap. This structure is similar to the double-barrier quantum-well structure for electrons .