Doctoral Thesis: Photoinduced Dynamics Studied by Ultrafast Single-Shot Pump-Probe Spectroscopy

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Event Speaker: 

Yu-Hsiang Cheng

Event Location: 

6-321

Event Date/Time: 

Friday, May 3, 2019 - 4:00pm

Abstract: 

This thesis focuses on the development of dual-echelon single-shot spectroscopy and its applications to study irreversible photoinduced dynamics. First, the ultrafast laser sources and the related controlling and characterization techniques are discussed. In particular, we have invented a two-stage dual-beam noncollinear optical parametric amplifier to provide tunable sources for pump-probe spectroscopy. Next, the experimental setup of dual-echelon single-shot spectroscopy is illustrated with great details. Possible noise sources and correction methods are explored. With single-shot spectroscopy, we studied photoinduced dynamics in three different materials. In bismuth, we found a transition into a transient symmetric phase at high fluences. We showed the coherent control of phonon parameters with pump-pump-probe experiments. We also simulated the carrier and phonon dynamics by a modified two-temperature model. In tellurium, we demonstrated the amorphization of crystalline tellurium induced by femtosecond pulses is a thermal process. We also estimated the lattice temperature by the change in phonon frequency. In a strained manganite film, we observed photoinduced persistent insulator-to-metal transition and showed the partial recovery of the generated metallic phase to the insulating phase.
 
Thesis Supervisor: Prof. Keith Nelson