具有亚波长带隙的晶格共振声子晶体

Lattice-resonant phononic crystals with subwavelength gaps

局域共振是已知的能形成声波亚波长带隙的机制,然而运用这种机制很难形成以液体为基体的亚波长带隙声子晶体.本文提出了一种新的形成亚波长带隙的机制,即晶格共振机制,它是一种非局域的共振机制,对应的声子晶体称为晶格共振声子晶体,研究发现这种声子晶体存在亚波长带隙.通过引入局域度的概念,本文解释了这两种机制的不同,获得了形成亚波长带隙更加普遍的条件.晶格共振机制使得以液体为基体的亚波长带隙声子晶体成为可能.

The local resonance mechanism is a renowned methodology for obtaining subwavelength gaps with respect to acoustic waves. In locally resonant phononic crystals, low-frequency acoustic waves are localized around scatters, and the hosts only provide weak interaction between scatters. However, it is difficult to obtain phononic crystals with subwavelength gaps using liquid hosts via the local resonance mechanism. In this paper, a new mechanism, i.e., the lattice resonance mechanism, is proposed for the formation of subwavelength gaps with respect to acoustic waves. The lattice resonance mechanism is a nonlocal resonance mechanism. The type of phononic crystal obtained based on this novel mechanism is called a lattice-resonant phononic crystal. Research results indicate the presence of omnidirectional and directional subwavelength gaps in lattice-resonant phononic crystals. However, the low-frequency waves in these phononic crystals are extended to whole lattices and not localized around scatters. The lattice resonance mechanism enables the formation of subwavelength gaps in phononic crystals with liquid hosts. By introducing the concept of degree of localization, more general conditions are obtained for the formation of subwavelength gaps in the case of acoustic waves. Further, the abnormal properties of the lattice-resonant phononic crystals are discovered and explained systematically. In addition, the acoustic impedances of the liquid hosts and lattice-resonant phononic crystals are considerably similar. This new type of phononic crystal can be used to control the low-frequency acoustic waves in hydroacoustic fields, where the locally resonant phononic crystals do not fit.