Experimental evidence of the non-transmission range enlargement in phononic heterostructures

Abstract

In this work we present experimental evidence of the enlargement of the non-transmission range in one-dimensional phononic crystal heterostructures. Heterostructures are composed by a tandem of different phononic crystal lattices. The constituent phononic crystal lattices have been properly chosen so that their band gaps overlap each other to obtain a giant stop band. Heterostructures consisting of a periodic arrangement of aluminum and epoxy layers were fabricated and characterized. We have designed giant stop bands in the range of MHz obtaining a good agreement between theoretical and experimental results.

Off-axis phonon and photon propagation in porous silicon superlattices studied by Brillouin spectroscopy and optical reflectance

“…(9) and (11) that when using a 180 -backscattering geometry, the frequency of the probed l ¼ 0 bulk modes are approximately independent of h i (recall that Eqs. (9) and (11) are approximations). For all other folded phonon branches, however, 2pl/D 6 ¼ 0 and, thus, the frequencies of the corresponding observed phonon modes, in general, depend on h i .…”

“…Multilayered mesoporous silicon films with a spatial modulation in the porosity, and hence in the elastic impedance, exhibit rich acoustic phonon band structures. [1][2][3][4][5][6][7][8][9][10] The resulting bulk acoustic dispersion curves contain multiple zone-folded branches which may be accompanied by the appearance of forbidden phonon frequency bands, or in analogy to photonic crystals, phononic band gaps. Recent ultrasonic measurements along the modulation direction of films with square-wave, 4,7 sinusoidal, 5 and linearly graded modulation 10 variations in the porosity have reported the existence of one-dimensional phononic band gaps in the bulk longitudinal acoustic phonon band structure; these band gaps were centered at frequencies on the order of 1 GHz.…”

“…Recent ultrasonic measurements along the modulation direction of films with square-wave, 4,7 sinusoidal, 5 and linearly graded modulation 10 variations in the porosity have reported the existence of one-dimensional phononic band gaps in the bulk longitudinal acoustic phonon band structure; these band gaps were centered at frequencies on the order of 1 GHz. Additionally, theoretical and experimental studies of stacked phononic crystal mirrors 6,9 have shown the existence of giant phononic band gaps in the MHz frequency range of these structures. As well, Brillouin light scattering studies on binary periodic porous silicon (p-Si) superlattices (SLs) showed a complex bulk longitudinal acoustic band structure, 3,8 with a second longitudinal mode branch observed for phonons directed along the superlattice modulation axis.…”