Excitations in Inhomogeneous Media
In this area, we focus on integrating modeling, simulation and experiments in linear (L) and non-linear (NL) acoustic phenomena in inhomogeneous media. Acoustics is finding a whole new range of applications in numerous industries and our knowledge of that field is being challenged by these new applications. In particular, the field of L and NL in inhomogeneous media is an emerging area of science and technology with broad industrial and medical applications, as well as applications in architectural design and with significant impact on human society. Sound waves are a major component of the way human beings interact with their environment. Controlled sound waves have had many general uses in industrial, laboratory processes and medical imaging. Sonication, or the irradiation of various media, is a non-chemical method of solubilization (e.g. dissolving large proteins), mixing (e.g. in bioreactors), cell poration (reversible permeabilization of cell membrane, irreversible lysation), driving chemical reactions, cleaning (e.g. megasonic cleaning in microelectronic manufacturing), etc. The interaction between ultrasounds and the highly inhomogeneous, viscoelastic medium that constitutes the human body is at the heart of ultrasound imaging. Sound is also noise and when uncontrolled it leads to significant “pollution” and degradation of the quality of life in urban environments. Acoustic waves are also omnipresent in telecommunication technologies such as those involved in sound emission and reception but also in surface acoustic wave or bulk acoustic wave-based radio frequency filters, etc. This non-exhaustive list of applications illustrates the critical role sound, sound control, sound-based technology have on current industry, health and people living conditions. Several important common features emerge from this list that need investigation. The structure of the medium through which the sound propagates is key to its control. These structures could be periodic (e.g. acoustic band gap materials) but also non-periodic, or hierarchical or multiscale (ranging from micrometer in telecommunication devices, microelectronics manufacturing or biological media to meters and tens of meters in architectural applications). These structures could be composed of solids, fluids (liquids or gases). In addition to elastic behavior, non-elastic effects associated with viscible fluids and solids or non-linear effects will have drastic impact on properties. Non-linear effects include acoustic streaming, cavitation, shock, etc. Overall, this is an immensely rich, interdisciplinary, field of science and engineering with important applications to industrial and societal problems.
Finally, through manipulation of the structure-property relationships in inhomogeneous composite media, materials with properties that cannot be found in nature can be designed, namely, the so-called metamaterials. Acoustic metamaterials that exhibit for instance negative refraction have the potential of leading to flat lenses and subwavelength-resolution imaging devices and systems.
Very recent work in this area has involved uncovering the analogies between the properties of elastic waves in inhomogenous elastic media and quantum mechanics. In particular we have addressed the possibility of achieving the properties of superposition of elastic waves analogous to pseudospin states. We have also uncovered the possibility of manipulating the phase of elastic waves to create operations analogous to quantum gates. Finally, the possibility of achieving non-separable elastic waves equivalent to the notion of classical "entanglement" open unique possibility in massive data storage and manipulation analogous to quantum computing.
Novel phenomena such as topological acoustics and phononics may lead to extraordinary functions such as non-reciprocal propagation of elastic waves and immunity to scattering.
In addition to phonon excitations, we have conducted research and continue to have interest in other types of excitations in inhomogeneous media such as photonic crystals and metametarials, plasmonics, electronic and magnetic excitations.
Photonic, Electronic, Magnetic, Vibrational Excitations