Fundamental physics has a special interest concerned with the localization phenomena of sound and vibrations in PCs. Researchers have prospected numerous applications based on cavity structures built around PCs, such as wave filters, #https://www.selleckchem.com/products/kpt-8602.html randurls[1|1|,|CHEM1|]# waveguides, and splitters [6–9]. Furthermore, it is possible to design cavities for coherent (single-wavelength) phonon generation and control, to attain phonon amplification and ‘lasing’ in the called ‘saser’, one of the most important potential applications [10–12]. Periodic solid-state structures exhibit transmission stop bands for waves at certain frequencies. By placing one or more defects into a perfect phononic crystal, acoustic cavities are created inside the

system. The presence of these defects, produces localization of elastic or acoustic modes inside the phononic band gap. These localized modes are the acoustic analog of donor or acceptor states produced inside the band gap of semiconductors. In analogy

with electronic systems, one can consider these acoustic states to control the sound propagation through the structure. If a defect is introduced into a periodic structure, the translational symmetry is broken and highly localized defect modes within the band gaps are created [6, 8, 13, 14]. Point, linear, and planar defect states have been theoretically investigated in one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) phononic crystals [3, 15, 16]. In 1D structures, a microcavity can be a spacer layer of thickness λ/2 enclosed by two Bragg reflectors [17]. In 2002, Trigo et

al. proposed phonon cavities in structures consisting of two learn more semiconductor superlattices enclosing a spacer layer, showing that acoustical phonons can be confined in such layered structures if the spacer triclocarban thickness is an integer multiple of the acoustic half-wavelength at the center of one of the superlattice-folded minigaps. These acoustic cavities are semiconductor multilayers in the nanometer scale and are fabricated by molecular beam epitaxy (MBE), which is a sophisticated and expensive technique that requires ultra-high vacuum system and a very tight control on the growth parameters, and modulate the thicknesses is easier than to modulate the elastic properties of the layers. Contrasting, porous silicon (PS) multilayer fabrication is relatively easy and considerably less costly, besides that this material allows to modulate both the thicknesses and the elastic properties of each layer. PS is known as a versatile material with applications in light emission, sensing, and photonic devices [18]. The possibility of producing acoustic band gaps in PS was proposed in 2005 [19], and detailed calculations of predicted bandwidths were subsequently published [20]. Recently, experimental results of Brillouin light scattering suggested the existence of zone-folded phonons and phononic band gaps in PS multilayers [21]. G. N. Aliev et al.