Broadband non-reciprocal transmission of sound with invariant frequency

Abstract

We design and experimentally demonstrate a broadband yet compact acoustic diode (AD) by using an acoustic nonlinear material and a pair of gain and lossy materials. Due to the capabilities of maintaining the original frequency and high forward transmission while blocking backscattered wave, our design is closer to the desired features of a perfect AD and is promising to play the essential diode-like role in realistic acoustic systems, such as ultrasound imaging, noise control and nondestructive testing. Furthermore, our design enables improving the sensitivity and the robustness of device simultaneously by tailoring an individual structural parameter. We envision our design will take a significant step towards the realization of applicable acoustic one-way devices, and inspire the research of non-reciprocal wave manipulation in other fields.

Tunable Asymmetric Transmission via Lossy Acoustic Metasurfaces

“…Recently, there has been a growing interest in exploring new physics by embracing the losses in acoustic systems. For example, parity-time symmetric acoustic materials with carefully tailored loss and/or gain have been theoretically and experimentally demonstrated for their ability of unidirectional cloaking [12,13], nonreciprocal reflection [14,15], unidirectional transmission [16], topological characteristics [17] and others [18,19]. This study, for the first time, theoretically and experimentally demonstrates asymmetric wave transmission in lossy acoustic gradient-index metasurfaces (GIM).…”

Nonreciprocal Surface Acoustic Waves in Multilayers with Magnetoelastic and Interfacial Dzyaloshinskii-Moriya Interactions

“…So far, the nonreciprocal propagation of SAW was found in devices with moving or rotating elements [7,8], where the effect of the summation of velocities of sound and moving media was used. An alternative way to achieve acoustic nonreciprocity is to use nonlinear effects in high-power acoustic waves, where the acoustic wave loss or gain are power-dependent [9][10][11][12]. Unfortunately, both these ways did not lead to the development of practical nonreciprocal devices based on acoustic waves.…”

Non-reciprocal elastic wave propagation in spatiotemporal periodic structures

“…Therefore, considerable efforts have been devoted to achieve non-reciprocal behavior through nonlinear or timemodulated devices. Indeed, giant non-reciprocal transmission can be obtained by combining a nonlinear medium with a superlattice (Liang et al 2009(Liang et al , 2010 or with a gain/loss pair (Gu et al 2016), hence exploiting asymmetric frequency conversion of the nonlinear medium due to second-harmonic generation (SHG) and frequency selectivity of sonic crystals. Experimental evidence shows rectifying ratios up to 10 4 , although efficacy of such nonlinear devices depends on the amplitude of the input signal, which has to be large enough to trigger the SHG mechanism of the nonlinear medium (Liang et al 2010).…”