Femtosecond Photoacoustic Equipment for Materials Characterization

摘要

The objective of this project was to configure non-contact nondestructive photo-acoustic measurement systems for characterization of micro- and nano-structured material systems including thin films and coatings. Specifically, a femtosecond photo-acoustic materials characterization facility has been established. At Northwestern University, we are actively pursuing research efforts to increase the sensitivity of photo-acoustic metrology. These efforts have led to advance: in laser-based ultrasonics, fiber-optic ultrasonic sensors, and photo-acoustic characterization of thin films. The femtoseconc photo-acoustic system has now extended our acoustic frequency reach to the Gigahertz range. Specific research projects that we are continuing to pursue include: transient grating and pump-probe photo-acoustic experiments on very thin films, MEMS devices, and nano-structured composites. Specific material and geometric properties that can be characterized using the photo-acoustics facility include: elastic moduli, thickness, and residual stress.