Broadband Nonreciprocal Acoustic Propagation Using Programmable Boundary Conditions: From Analytical Modeling to Experimental Implementation

Abstract

In this paper, we theoretically, numerically and experimentally demonstrate the acoustic isolator effect in a 1D waveguide with direction dependent controlled boundary conditions. A theoretical model is used to explain the principle of non reciprocal propagation in boundary controlled waveguides. Numerical simulations are carried out on a reduced model to show the non-reciprocity as well as the passivity of the system, through the computation of the scattering matrix and the power delivered by the system. Finally, an experimental implementation validate the potential of programmable boundary conditions for non reciprocal propagation.

Dynamics and topology of non-Hermitian elastic lattices with non-local feedback control interactions

“…Among the key results, we demonstrate non-reciprocity associated with attenuation and amplification for waves propagating in different directions in 1D and 2D lattices, along with their topological properties associated with winding number of the complex dispersion bands, and localization of bulk modes at edges and corners. While idealized spring-mass lattices where used herein to elucidate the fundamental properties of elastic media with feedback interactions, we highlight that already existing platforms used to experimentally realize active materials with time-modulated properties [32][33][34][35][36] may potentially be modified to support feedback interactions of the type introduced here. The presented results open new possibilities for the design of active meta materials with novel functionalities such as those related to selective wave filtering, splitting, amplification and localization, both in one and two dimensions.…”

“…Topological states have been successfully observed in several platforms [13][14][15][16][17][18][19][20][21], and have been pursued to achieve robust, diffraction-free wave motion. Additional functionalities have been explored in the context of topological pumping [22][23][24][25][26], quasi-periodicity [27][28][29], and non-reciprocal wave propagation in active [30][31][32][33][34][35][36] or passive non-linear [37][38][39][40] systems. These works and the references therein illustrate a wealth of strategies for the manipulation of elastic and acoustic waves, and suggest intriguing possibilities for technological applications in acoustic devices, sensing, energy harvesting, among others.…”

Omindirectional Non-Reciprocity via 2D Modulated Radial Sonic Crystals

“…Θ n e in(κ r r−ω r t) (8) which corresponds to the space-varying configuration, augmented by a temporal modulation with angular frequency ω r = 2π/T r . T r is the temporal period.…”

“…Dispersion properties showing lack of mirror symmetry in the wavevector space witness the breaking of such principle, implying directional propagation characteristics. The breaking of reciprocity is considered an interesting topic within the research community and is motivated by numerous applications of technological relevance for different realms of physics, such as mechanical [1][2][3][4][5][6], acoustic [7][8][9], and electromagnetic [10] systems. In this context, one dimensional space-time modulations have been successfully conceived to generate filtering bands (or bandgaps ) occurring at different frequencies for counter propagating waves.…”

“…Similarly, passive beams with embedded resonators have been used for this purpose, by properly phase shifting consecutive modulation signals, mimicking a plane wave propagation along the beam's dimension [13][14][15]. The acoustic counterpart has been studied by Cummer and co-workers [7,16,17] and S. Karkar et al [8], among others [18,19], demonstrating strong nonreciprocal transmission of acoustic waves. In addition, nonreciprocity in modulated electromagnetic waveguides have been object of research in the last years, with emphasis on Bloch modes conversion [20,21] and stability [22,23].…”