PhD defence by Dmitry V. Khakhulin – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2010 > PhD defence by Dmitry ...

PhD defence by Dmitry V. Khakhulin

Recent development of pulsed optical and x-ray sources has brought great opportunities for time-resolved investigations on laser radiation induced processes in matter. In particular, available techniques are capable of dynamical studies on coherently excited acoustic phonons in nanostructures on characteristic (sub)picosecond timescales. Combination of purely optical and x-ray based pump-probe techniques allows for deeper understanding of transient thermal and mechanical properties of the materials.

The thesis addresses development, optimization and application of tabletop instrumentation for ultrafast optical reflectivity and x-ray diffraction experiments. The x-ray diffraction setup is based on an ultrashort laser driven x-ray diode providing picosecond hard x-ray pulses at kilohertz and megahertz repetition rates. Presented experimental results include detection of laser induced eigen vibrations in metal films and semiconductor nanowires using both the optical and the x-ray probes. Some attention is paid to numerical modeling of such acoustic modes in view of different excitation mechanisms. Finally, optical detection of longitudinal and shear strain pulses propagation in thin films of organic semiconductor is demonstrated by means of picosecond acoustic interferometry.

PhD defence by Dmitry V. Khakhulin