CAJ | 학술논문

电子二极管的发明标志着现代电子学的诞生，在整个人类社会中引起了科技的深刻变革。声波是一种具有非常悠久的研究历史的经典波，却始终被认为仅具有对称的传播形式。若能制造出可像电子二极管控制电流般实现声波单向导通的声学器件，显然将对整个声学研究领域产生重大影响，具有重要的科学意义及应用价值。第一个基于非线性媒质与声子晶体的声二极管利用非线性突破声学互易原理的局限，首次实现了将声能流限制在单一方向上的声整流效应。针对非线性系统转换效率低下的固有缺陷，在线性体系内围绕声单向传播这个重要科学问题开展了一系列理论和实验研究，设计与制备了多种具有特殊结构和性能的线性声学单向结构，在器件的效率、带宽及尺寸方面产生了突破。在声二极管研究的基础上，第一个可以像电子三极管操控电流般对声流进行操控与放大的声三极管理论模型也被提出。本文介绍了声单向传播这一新兴且富有蓬勃生机的研究领域中的主要进展。
전자이겁관적발명표지착현대전자학적탄생，재정개인류사회중인기료과기적심각변혁。성파시일충구유비상유구적연구역사적경전파，각시종피인위부구유대칭적전파형식。약능제조출가상전자이겁관공제전류반실현성파단향도통적성학기건，현연장대정개성학연구영역산생중대영향，구유중요적과학의의급응용개치。제일개기우비선성매질여성자정체적성이겁관이용비선성돌파성학호역원리적국한，수차실현료장성능류한제재단일방향상적성정류효응。침대비선성계통전환효솔저하적고유결함，재선성체계내위요성단향전파저개중요과학문제개전료일계렬이론화실험연구，설계여제비료다충구유특수결구화성능적선성성학단향결구，재기건적효솔、대관급척촌방면산생료돌파。재성이겁관연구적기출상，제일개가이상전자삼겁관조공전류반대성류진행조공여방대적성삼겁관이론모형야피제출。본문개소료성단향전파저일신흥차부유봉발생궤적연구영역중적주요진전。
Realizations of one-way manipulations in various kinds of energy flux are always highly desirable. The most famous example should be the invention of electric diodes which marked the emergence of modern electronics and resulted in worldwide technology revolutions. Acoustic wave, albeit a classical wave with much longer research history in comparison with the electricity, has long been thought to propagate easily along two opposite directions in any path. Hence it should be intriguing to realize the one-way transmission of acoustic waves by designing the acoustical analogy of electric diodes, which would have deep implications in all the acoustics-based applications and the field of acoustics in general. In this review, we briefly describe recent advances in acoustic one-way manipulation which has become a new frontier of science and is of remarkable significance in both the physics and engineering communities. The emergence of the first“acoustic diode”, formed by coupling a phononic crystal (PC) with a nonlinear medium, offers the possibility of rectifying acoustic energy flux by breaking through the barrier of reciprocity principle via the introduction of nonlinearity. Despite of the efforts in enhancing the performances of nonlinear acoustic diodes by updating their structures, the inherent shortcomings in nonlinear systems such as low e?ciency and narrow bandwidth still attract considerable attentions on the potential of linear structures, aiming at constructing a one-way manipulation on particular modes of an acoustic wave without breaking the reciprocity principle. A series of linear acoustic one-way devices have already been designed and fabricated with significantly improved performances. On the basis of asymmetric mode conversion, a linear one-way plate for Lamb waves is designed. High e?cient one-way transmission for plane waves propagating along two opposite directions is realized by coupling a PC and a diffraction structure. Unidirectional waveguide is designed and fabricated which only allows for a plane wave incident from one of the two openings to pass. A unidirectional structure with a total thickness as thin as the wavelength is realized by reconstructing the otherwise plane wavefront with acoustic gratings. An acoustic gradient-index structure is proposed that can directly manipulate the wave trajectory asymmetrically and then yield asymmetric acoustic transmission within a considerably broad band. Acoustic metamaterials with near-zero indexes have also been employed to realize unidirectional transmission with a controllable transmitting angle and consistent wavefront. These advances are important steps towards the practical applications which generally require integration and minimization of devices having high e?ciency and broad bandwidth. The recently emerged “acoustic transistor”has been described as well, which can be regarded as the acoustical counterpart of an electric transistor and enables the amplification and switch of acoustic waves by an acoustic wave, or by exploiting the three-wave mixing effect. We also discuss the challenge and promise of the usage of acoustic one-way devices in controlling acoustic waves.