Publication Date:
2016-07-13
Description:
Author(s): G. P. Ward, A. P. Hibbins, J. R. Sambles, and J. D. Smith Arrays of subwavelength slit cavities have been of interest to the acoustic metamaterial community for some years now, giving rise to such phenomena as “enhanced acoustic transmission”, where sound of certain wavelengths can transmit through the slit array structure as if it were not there. This behaviour is widely accepted as a coupling effect between diffraction evanescent waves arising from structure factor, and Fabry-Perot like resonances supported along the length of each slit cavity. Here, the authors explore the effect of altering the spacing, or width, of some of the slits that form the array, thereby forming a “compound” grating, where each periodic unit cell is comprised of multiple slit cavities. The transmission of such structures is experimentally recorded, where it is found that as one increases the number of slit cavities per unit cell, broad and deep minima can appear in the peaks of the primary enhanced acoustic transmission resonance that may have a strong angular dependence. These features owe their existence to the “phase resonance”, where new degrees of freedom available to the near field allow adjacent slit cavities to be out-of-phase with one another and thus destructively interfere with the re-radiated pressure wave. Such behaviour has been studied extensively in the electromagnetic case, where a surface wave band folding picture could be used to predict the dispersive nature of these phase resonances. A similar explanation of the underlying surface wave physics is extended here to the acoustic case. [Phys. Rev. B 94, 024304] Published Tue Jul 12, 2016
Keywords:
Dynamics, dynamical systems, lattice effects
Print ISSN:
1098-0121
Electronic ISSN:
1095-3795
Topics:
Physics
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