Propagation of sound beams behind sonic crystals

Formation of collimated beams behind the woodpile photonic crystal

“…The character of the beam propagation behind the PhC depends on the wave front of the self-collimated beam. In particular, if the wave front of the beam acquires positive curvature (due to propagation in a material with negative or anomalous diffraction), then the beams can be focalized behind the modulated media [17]. The effect is related to superlensing (see [18] for theory and [19] for experiments in 2D PhCs, resulting in imaging of point sources by a PhC slice).…”

Angular Band Gaps in Sonic Crystals: Evanescent Waves and Spatial Complex Dispersion Relation

“…In addition to BG in the band structure (spectral dispersion relation), the periodic structure can also modify the spatial dispersion, allowing the managing of the diffractive broadening of beams [32,35,36]. The interaction of the spatial spectrum of the incident wave with the isofrequency curves of the modulated material can produce different focusing regimes depending on the curvature of the isolines in k-space, one example is the self-collimation discussed above.…”

“…Due to that, one can observe different behaviour depending on the spatial dispersion relation, i.e., on the curvature of the isofrequency contours [32]. The socalled self-collimation effect, due to flat isofrequency contours, consists in the propagation of a beam in the periodic system without apparent diffraction keeping its original size.…”

Broadband Transmission Loss Using the Overlap of Resonances in 3D Sonic Crystals

“…The band gaps appear at high symmetry points in the Brillouin zone due to the presence of a degeneracy of the band structure produced by the Bragg interferences in the diffractive regime (λ a/2, λ being the wavelength of the incident wave and a the lattice constant characterizing the periodicity of the structure). Many interesting physical phenomena arise from this particular dispersion relation such as wave localization [2,3], excitation of evanescent waves [4,5], and relevant applications concerns filtering [6] and wave guiding [7][8][9]. In particular, many approaches have been proposed to degenerate the band and thus enlarge the band gaps [10][11][12].…”