| Semiconductor superlattices are well known as periodically modulated stacks to modify and control electronic and photonic properties in bulk materials and to design novel functionalities for transport and optoelectronic devices, including Bloch oscillation or strong coupling for exciton polaritons in microcavities. In this talk, we will describe some new ideas, developed in the past few years, to transfer these concepts in the fields of acoustic phonons in multilayers. We will shortly recall the concept of folded acoustic phonons in superlattices and focus on the recently demonstrated acoustic nanocavities. We will report theoretical analysis in the elastic approximation and experimental results by high resolution Raman scattering and femtosecond pump-probe transient reflectivity, focusing on the study of the linewidth and escape time of cavity phonons and the possibility to modify these properties with non-periodic mirrors. We will also discuss the modification due to the inclusion of acoustic nanocavities inside photonic microcavities or to the association of identical of graded cavities to design acoustic molecules and acoustic analogues of Bloch oscillators. |
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