《Controlling the optical properties of solids with acoustic waves》
Illustration of the exciton of TiO2 interacting with a propagating coherent acoustic wave. Credit: Adriel Dominguez (Max Planck Institute, Hamburg)Physicists from Switzerland, Germany, and France have found that large-amplitude acoustic waves, launched by ultrashort laser pulses, can dynamically manipulate the optical response of semiconductors..
IMAGE:Illustration of the exciton of TiO2 interacting with a propagating coherent acoustic wave. Image credit:Adriel Dominguez (Max Planck Institute, Hamburg) One of the main challenges in materials science research is to achieve high tunability of the optical properties of semiconductors at room temperature. These properties are governed by "excitons", which are bound pairs of negative electrons and positive holes in a semiconductor. Excitons have become increasingly important...
In situmeasurements of compressional and shear wave speed and attenuation were collected 30 cm below the water-sediment interface in Currituck Sound, North Carolina at two field locations having distinctly different sediment types: medium-to-fine-grained sand and fine-grained sand with approximately 10% mud content. Shear wave measurements were performed with bimorph transducers to generate and receive horizontally polarized shear waves in the 300 Hz to 1 kHz band, and compressional wave measurements were performed using hydrophones operated in the 5 kHz to 100 kHz band. Sediment samples were collected at both measurement sites and later analyzed in the laboratory to characterize the sediment grain size distribution for each field location. Compressional and shear wave speed and attenuation were estimated from the acoustic measurements, and preliminary comparisons to the extended Biot model by Chotiros and Isakson [J. Acoust. Soc. 135, 3264–3279 (2014)] and the viscous grain-shearing theory by Buckingham [J. Acoust. Soc. 136, 2478–2488 (2014)] were performed.