Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density ...

We provide evidence that internal waves cause frequent vertical migrations (FVM) in fishes. Acoustic data from the Benguela Current revealed that pelagic scattering layers of fish below ~140 m moved in opposite phases to internal waves, ascending ~20 m towards the wave trough and descending from the wave crest. At the trough, the downward displacement of upper waters and the upward migration of...

Picosecond laser ultrasonic techniques for acoustic wave generation and detection have been employed to probe shear acoustic waves in liquid glycerol at gigahertz frequencies. The experimental approach uses a unique laser pulse shaping technique and a crystallographically canted metal layer to generate frequency-tunable transverse acoustic waves, and uses time-domain coherent Brillouin scatteri...

Techniques for investigating acoustic backscatter from anisotropic biological tissues are examined. This empirical study combines single-scatter theory with the known elastic properties and histology of the renal cortex to predict the backscatter coefficient from kidney parenchyma. A transverse isotropic correlation model is developed to explain how backscattered energy, which varies with the i...

The finite-difference time-domain method is a simple but powerful numerical method for simulating full-wave acoustic propagation and scattering. However, the method can demand a large amount of computational resources. Traditionally, continuously curved boundaries are represented in a stair-step fashion and thus accurately modeling scattering from a boundary will require a finer discretization ...

In a theoretical design study, we propose buried waveguides made of germanium or alloys of germanium and other group-IV elements as a CMOS-compatible platform for robust, high-gain stimulated Brillouin scattering (SBS) applications in the mid-infrared regime. To this end, we present numerical calculations for backward-SBS at 4 μm in germanium waveguides that are buried in silicon nitride. Due t...

Computational time reversal imaging can be used to locate the position of multiple scatterers in a known background medium. Here, we discuss a sparse approximation method for computational time-reversal imaging. The method is formulated entirely in the frequency domain, and besides imaging it can also be used for denoising, and to determine the magnitude of the scattering coefficients in the pr...

2014 Tanane exhibits at Tc = 287 K an order-disorder phase transition associated with an inversion motion of polar molecules. The linear coupling between the molecular ordering and the shear strain uxy results in soft transverse acoustic modes (Tx[010] and Ty[100]) whose low frequency study is reported in the second part of this

Control of parametric laser-plasma interactions (LPI) is essential to the success of inertial confinement fusion (ICF). Through a research collaboration with the Los Alamos National Laboratory (LANL), we have had the opportunity to participate in world-class laser-plasma experiments. The goal of these experiments was to gain a fundamental understanding of LPI by studying the interaction of a si...

Introduction The damping rate of ion-acoustic waves in plasma plays an important role in establishing the threshold for the onset of stimulated Brillouin scattering, ion-temperature-gradient instability, current-driven ion-acoustic instability, and other drift-wave microinstabilities. The effect of electron-ion (ei) collisions on the ion-acoustic damping rate has been recently investigated by a...