Porous silicon phononic crystals

Abstract

Work on phononic crystals in porous silicon is first put in context of the more general interest in controlling wave behavior in periodic media in both photonic and phononic crystals. The condition for a stop band for acoustic waves is derived by analogy with the Bragg condition with optical multilayers and then also obtained from the Rytov theory of layered acoustic media. The modeled acoustic bandgap in porous silicon is then defined and examined with the parameters used to model acoustic velocities in the material. A historical overview of papers covering theory and experiments on acoustic bandgaps in porous silicon is then given with an emphasis on their hypersonic nature and phoxonic properties. Finally, applications of acoustic distributed Bragg reflectors (ADBRs) with integrated transducers for high-performance bulk acoustic resonators (BAW) and possible applications for thermoelectric devices are presented.