Non-degenerate two-photon absorption in bulk ZnSe, GaAs and Si
The two-photon absorption is a nonlinear optical process with various properties which makes it an excellent basis for a wide range of different applications. In this thesis the non-degenerate two-photon absorption coeffi‑cient β (ħω1, ħω2) as a function of the frequency ratio ω1/ω2 of the two driving fields is experimentally investigated whereby the sum energy ħω1+ħω2 is kept constant. The studied materials are the prototypical semiconductors ZnSe, GaAs and Si. Regardless of the direct or indirect character of the bandgap, the two-photon absorption strength increases with increasing ratio ω1/ω2 ≥1. The experimental data of ZnSe and GaAs agrees well with corresponding theoretical predictions for direct semiconductors. Si shows overall smaller absorption strengths. These results also agree with theoretical predictions for indirect semiconductors. In addition, different crystallographic orientations of the samples and polarization configurations of the two driving fields are analyzed. These results make an important contribution to the so far rarely investigated orientation and polarization anisotropy of the non-degenerate two-photon absorption.
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The campus of the Technical University of Dortmund is located near the freeway junction Dortmund West, where the Sauerland line A45 crosses the Ruhr expressway B1/A40. The Dortmund-Eichlinghofen exit on the A45 leads to the South Campus, the Dortmund-Dorstfeld exit on the A40 leads to the North Campus. The university is signposted at both exits.
The "Dortmund Universität" S-Bahn station is located directly on the North Campus. From there, the S-Bahn line S1 runs every 20 or 30 minutes to Dortmund main station and in the opposite direction to Düsseldorf main station via Bochum, Essen and Duisburg. In addition, the university can be reached by bus lines 445, 447 and 462. Timetable information can be found on the homepage of the Rhine-Ruhr transport association, and DSW21 also offer an interactive route network map.
One of the landmarks of the TU Dortmund is the H-Bahn. Line 1 runs every 10 minutes between Dortmund Eichlinghofen and the Technology Center via Campus South and Dortmund University S, while Line 2 commutes every 5 minutes between Campus North and Campus South. It covers this distance in two minutes.
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The facilities of TU Dortmund University are spread over two campuses, the larger Campus North and the smaller Campus South. Additionally, some areas of the university are located in the adjacent "Technologiepark".Zum Lageplan