Dresden 2020 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 15: Postersession KFM
KFM 15.6: Poster
Donnerstag, 19. März 2020, 16:00–18:30, P2/1OG
Light-induced absorption in Fe:LN by means of ns-pump supercontinuum-probe spectroscopy — •Bjoern Bourdon, Simon Messerschmidt, David Brinkmann, Andreas Krampf, Laura Vittadello, and Mirco Imlau — Department of Physics, Osnabrueck University, Osnabrueck, Germany
Pulse-induced transient absorption (TA) phenomena in iron doped lithium niobate, such as green-induced infrared absorption or green-induced blue-absorption, play an important role in laser-induced damage and are commonly attributed to the absorption features of small polarons. However, only recently, Messerschmidt [S. Messerschmidt, J. Phys. Condens. Matter, 31 (2019)] has proposed a revised model taking the presence of long-lived excitonic states bound to FeLi centers into account. We here investigate the pulse-induced TA by means of ns-pump supercontinuum-probe spectroscopy in the time range from 10−7−102 s with the goal to control and probe the blue absorption feature related with these excitonic states. For this purpose, three distinct experimental configurations are investigated that enable targeted optical injection of electron-hole-pairs at Nb5+−O2−-octahedra in direct vicinity of FeLi and a clear separation from the well-known small polaron absorption bands. As a result, the optical fingerprint of the FeLi2+−O− − VLi excitonic state is deduced revealing a broad-band absorption feature (total width: 1.2 eV) with two peaks at 2.2 eV and 3.0 eV and a maximum absorption cross-section of up to σ (2.85 eV) = (4 ± 2)· 10−22 m2. Financial support (DFG INST 190/165-1 FUGG, DFG IM37/11-1) is gratefully acknowledged.