title: Acoustic asymmetric transmission based on time-dependent dynamical scattering.
abstract: An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade's rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies.
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Ni
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Ye-Long
authors.initials: YL
authors.lastname: Xu
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Xiao-Chen
authors.initials: XC
authors.lastname: Sun
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Ze-Guo
authors.initials: ZG
authors.lastname: Chen
authors.affiliation: Department of Electrical Engineering, The State University of New York at Buffalo, Buffalo, NY 14260, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Feng
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Xiao-ping
authors.initials: XP
authors.lastname: Liu
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Lu
authors.affiliation: National Laboratory of Solid State Microstructures &Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Yan-Feng
authors.initials: YF
authors.lastname: Chen