Ultrafast spatio-temporal mapping of gigahertz lattice distortion in a ferroelectric crystal (Conference Presentation)
We capture the spatio-temporal oscillations within large individual ferroelectric domains and across domain walls upon optical excitation in a single crystal of BaTiO3 with ~350 nm lateral resolution and ~100 ps temporal resolution using synchrotron x-ray pulses as probes. Spatially resolved ultrafast mapping across domain walls reveals that the optical excitation pump can generate GHz acoustic standing waves of different frequencies between the surface and buried domain wall interfaces at different depths. Phase-field simulations reveal that a thermo-electro-acoustic mechanism can quantitatively explain the observed dynamics. The study reveals the importance of combined spatial and temporal resolution for understanding ultrafast dynamics in inhomogeneous microstructures.
We developed a 3D model to simulate the radar image formation process of natural surfaces. This 3D model is divided into two main parts. First, the radar system is modeled using a 3D point spread function (PSF). Second, the observed terrain is modeled using 3D randomly distributed scatterers as well as predetermined scatterer positions. The image formation process involved the convolution of the PSF with the terrain model, the extraction of signal envelope and sampling in the range and azimuthal directions. To enhance the computing efficiency of the convolution process we transpose the problem into the Fourier domain. Our 3D model is useful to study the parameters involved in the formation and the analysis of radar images.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.