Wave Physics of Complex Mesoscopic Materials

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Waves in complex media exhibit remarkable properties, many of which result from strong multiple scattering and which continue to challenge our basic understanding of wave physics. This subject underpins many scientific and engineering disciplines that rely on wave-based techniques for imaging and materials characterization. The transport of waves through complex media is also fundamental to our prosperity, as it affects, for example, our ability to image complex structures (e.g., defects in concrete bridges and technological devices) and to effectively prospect for and extract natural resources. The goals of my research program are to build on recent progress in my laboratory to address the most important unresolved questions in the wave physics of complex strongly scattering materials, and to develop and use new techniques, based on our knowledge of wave scattering, to probe their structure and dynamics. To achieve these objectives, my students, postdoctoral fellow and I will perform state-of-the-art ultrasonic experiments, using techniques that we have pioneered and that are recognized internationally as some of the most powerful approaches to addressing many key challenges in the field. Our approach has many distinct advantages: the ability to record complete information about wave transport, the excellent resolution in space, time and frequency with which ultrasonic measurements can be performed, the feasibility of studying materials with precisely determined structures, the convenient range of lengths and times involved, and the likelihood of success in interpreting our data using new theoretical models. Examples of intriguing wave phenomena that we will investigate include Anderson localization (the ultimate trapping of waves due to disorder) and the remarkable properties of artificially structured materials (phononic crystals and metamaterials) due to negative refraction and topological effects. We will also develop dynamic imaging methods for complex media (in which traditional imaging techniques fail), leading to new ultrasonic spectroscopies for materials characterization and process control. We will use these techniques to study porous and granular materials, metamaterials with deeply subwavelength structures, foams, bubbly gels, and aerated model food biomaterials. The universality of wave behaviour across a huge range of wavelengths and wave types implies that the impact of our research is expected to extend well beyond ultrasonics, facilitating advances in other fields of research.