RESUMO
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
RESUMO
A thin copper sheet, populated by an array of complementary split ring resonators, presents strong surface wave beaming in orthogonal directions at two distinct frequencies. This simple array is significantly thinner than existing single frequency beaming surfaces. The observed beaming frequencies are associated with the two lowest resonance modes of the split rings, and the beams are subwavelength in width and approximately non-diverging. The beaming is analysed through comparison of near-field scans of the surface-normal electric fields with numerical simulations.
RESUMO
We study the radiative and bound acoustic modes supported by a rigid grating formed of three same-depth, narrow grooves per unit cell. One of the grooves is twice the width of the other two, forming a 'compound' grating. The structure supports so-called 'phase' resonances where the phase difference of the pressure field between the grooves on resonance varies by multiples of π. We explore the dispersion of these modes experimentally by monitoring the specularly reflected signal as a function of the angle of incidence. In addition, by near-field excitation, the dispersion of the non-radiative surface modes has been characterised. Our results are compared with the predictions of a finite element method model.