Μελέτη υψίσυχνων ελαστικών κυμάτων σε διαστρωματωμένα υλικά μετάλλου/πυριτίου με τη χρήση υπερβραχέων παλμών laser (Doctoral thesis)

Τζιανάκη, Ειρήνη

The objective of the current PhD thesis is the generation and detection of high frequency elastic waves in layered Metal/Silicon samples by femtosecond laser pulses. Specifically, in current study with femtosecond laser pulses of central wavelength λ=795nm a detailed study is performed of the thin metal films characteristics in order to produce high frequency and giant elastic waves that propagate inside Si substrate. For this purpose, a pump – probe transient reflectivity experimental setup was developed that Ti/Si and Ag/Si samples were examined, with different metal film thicknesses as well as a theoretical thermomechanical model – based on Extended Two Temperature Model – was also developed for the support of the experimental findings. The experimental and theoretical results of this thesis converge well in the generation of giant and ultrafast elastic waves when Ti is used as the optoelastic transducer. Furthermore, an optical control of the generated elastic waves was performed through the modification of the chirp of the femtosecond laser pulses. The results show the generation of higher elastic waves when negatively chirped laser pulses are used, comparing with positively chirped laser pulses. Additionaly, the theoretical model is further extended in order to include the chirp of the ultrashort laser pulses and the theoretical results converge well with experimental results.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Φυσικής
Subject classification: Ελαστικά κύματα
Keywords: Υπερβραχείς παλμοί laser,Μεταφορά θερμότητας,Μεταλλικά φιλμ
URI: https://olympias.lib.uoi.gr/jspui/handle/123456789/27763
http://dx.doi.org/10.26268/heal.uoi.3321
Appears in Collections:Διδακτορικές Διατριβές

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