Morten Willatzen, Professor,Department of Photonics Engineering, Technical University of Denmark
A discussion of two novel and exciting phenomena in acoustic structures is presented.
The first part presents the coupling of piezoelectric equations and semiconductor drift-diffusion equations and demonstrates in the plasmon frequency range where the permittivity approaches zero that large acoustic gains can be achieved under the action of a constant electric field by virtue of the Cherenkov effect. The gain can be several orders of magnitude. Device structures for acoustic amplification are also demonstrated theoretically.
The second part of the talk is a demonstration of highly effective acoustic absorbers consisting of porous lamella-air structures and that the absorption becomes higher for less than 100% filling fraction of the porous material. Results are compared with experiments that verify the result and the strong absorption is shown to stem from strong delay times of acoustic propagation.
Biography
Morten Willatzen is Deputy Director and Professor at the Department of Photonics Engineering, Technical University of Denmark since 2012. He received his PhD from the Niels Bohr Institute at the University of Copenhagen and held positions at Aarhus University, Max-Planck-Institute for Solid State Research, Germany, and as a Senior Scientist at Danfoss A/S, DK. In 2000 he became Associate Professor and 2004-2012 Full Professor in Mathematical Modelling at the Mads Clausen Institute, University of Southern Denmark. Morten Willatzen's research interests include solid state physics, mathematical physics, metamaterials and flow acoustics.
时间：Aug. 179:30 ~11:00.
地点：教一 411