The Study of Shock Waves and Laser Excited Lattice Dynamics using Ultrafast X-ray Diffraction

We have studied the picosecond lattice dynamics of optically pumped hexagonal manganite LuMnO3 using ultrafast x-ray diffraction. The results show a shift and broadening of the diffraction curve due to the stimulated lattice expansion. To understand the transient response of the lattice, the measured time- and angle-resolved diffraction curves are compared with a theoretical calculation based on dynamical diffraction theory modified for the hexagonal crystal structure of LuMnO3. Our simulations reveal that a large coupling coefficient between the a-b plane and the c-axis (c13) is required to the data. We compare this result to our previous coherent phonon studies of LuMnO3 using optical pump-probe spectroscopy. We have also performed preliminary experiments of shock waves traversing thin (approximately one micron) metal single-crystals, characterizing the shock wave using ultrafast spatial interferometry and with ultrafast x-ray diffraction. A summary of our current results will be presented.