講演題目：　Ultrafast Laser-generated Coherent Waves in Advanced Materials: From the Academic Lab to the Real World and Back

講　師　：　Keith A. Nelson教授
　　　　　（MIT）

日　時　：　平成１０年１１月１１日（水）午後 2：00より
場　所　：　電子科学研究所講堂（事務棟　2F）

要　旨　：
Coherent waves are generated and monitored optically in bulk and thin film materials to provide fundamental insight into their structures and dynamics; to exert optical control over their behavior; and to provide information ofimmediate practical value. On picosecond and nanosecond time scales, acoustic waves are characterized to learn about structural phase transitions and relaxation dynamics in crystals, polymers, and viscous liquids. In thin films, the measured acoustic responses yield the film elastic moduli, thermal diffusivities, and thicknesses, as well as a simple check for film-substrate delamination. This has led to the successful commercialization of the measurement method which is now used in the microelectronics industry. In ferroelectric crystalline solids, high-frequency vibrational waves which move through the lattice at a significant fraction of the speed of light are generated with femtosecond pulses and pulse sequences. Their responses teach us about ferroelectric phase transitions, anharmonic potential energy surfaces and nonlinear lattice dynamics, and the prospects for optical control over collective material behavior. The results illustrate the interplay between fundamental spectroscopic research on complex materials and the practical applications that may emerge.

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