Linear and nonlinear photo-acoustic spectroscopy with extreme ultraviolet radiation

Photo-Acoustic spectroscopy is a universally used method for determining material parameters in condensed matter systems. This experimental method relies on laser excitation and the subsequent frequency domain measurement of acoustic phenomenon. Within the last two decades, ultrafast lasers have been employed within the framework of photo-acoustic spectroscopy to study the time evolution characteristics of these acoustic phenomenon. Ultrafast lasers are currently being used in studying acoustic dynamics in both fundamental and applied research.; The present work contains experimental results wherein ultrafast Extreme Ultraviolet (EUV) Radiation has been incorporated into photo-acoustic spectroscopy for the first time. The use of ultrafast EUV radiation in studying acoustic dynamics exhibits high signal-to-noise ratios and high sensitivity to surface corrugation. Both of these features are directly attributable to the reduced probing wavelength of EUV, where even sub-nanometer topological changes in the sample induce large phase changes for EUV radiation.; The experimental results fall into two categories. The first of these are experiments performed on heterostructured samples, where uniform optical irradiation induces dynamics due to the differing material properties of the structure. These experiments were used as an introduction to acoustic spectroscopy with EUV and facilitated the measurement of signal-to-noise and surface sensitivity. The second set of experiments were performed on homogeneous samples where the excitation of acoustic behavior was done using the transient grating geometry. Periodically modulated surface excitation led to the generation and subsequent propagation of narrow band surface acoustic waves (SAW). These experiments approach the highest frequency SAWs ever generated using the transient grating technique.