Berlin 2018 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 27: Postersession KFM
KFM 27.10: Poster
Donnerstag, 15. März 2018, 15:00–17:00, Poster E
Broadband transient absorption spectroscopy of reduced lithium niobate after pulse excitation — •Stefan Hagedorn, Simon Messerschmidt, and Mirco Imlau — Department of Physics, Osnabrück University, Barbarastr. 7, 49076 Osnabrück, Germany
It is well known that transient absorption in lithium niobate (LN) can be studied by the use of single line pump and probe laser pulses [Imlau, M. et al., Appl. Phys. Rev. 2 (2015)]. However, this technique inhibits access to the specific broadband absorption features of the underlying polaron species.
We have addressed this problem by installing a transient absorption spectrometer with a ns pulse laser as excitation source and a ns supercontinuum pulse laser (λ=(400−1600) nm) as a probing source. Our setup is able to obtain temporal dynamics in the orders (10−7−103) s using an electronic delay between pump and probe pulses. For the first time we are able to show that the induced change of absorption in thermally reduced LN exhibit a transparency in the blue spectral region due to the depleted bipolarons and a significant absorption in the near-infrared induced by bound polarons. However, absorption maxima and minima are shifted from their denominated wavelengths compared to state of the art-knowledge. Using this setup, it is now possible to experimentally determine spectro-temporal absorption characteristics, e.g., to resolve polaron energy shifts caused by different pump wavelengths. This way, new insights to polaron dynamics beyond simplistic model extrapolations can be accessed. Financial support by the DFG (IM 37/5-2, INST 190/165-1 FUGG) is gratefully acknowledged.