Dresden 2020 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 15: Postersession KFM
KFM 15.4: Poster
Donnerstag, 19. März 2020, 16:00–18:30, P2/1OG
Enhancement of grating recording with sub-ps, near-infrared laser pulses at 1.6 µm in iron-doped lithium niobate — •Janina Ringel1, Bjoern Bourdon1, Felix Freytag1, Mirco Imlau1, Alexandr Shumelyuk2, and Serguey Odoulov2 — 1Department of Physics, Osnabrueck University, Osnabrueck, Germany — 2Institute of Physics, National Academy of Sciences, Kyiv, Ukraine
Recording of long-lived photorefractive gratings in the near-infrared, e.g. at a wavelength of λ = 1.6 µm, is commonly highly inefficient in Fe:LiNbO3, but can be sufficiently enhanced by means of temporally and spatially synchronized gate pulses. However, nothing is known about the underlying photophysical mechanism that enables diffraction efficiencies of up to 25 % so far. Here, we adress this question by studying the role of the gate light photon energy using trains of sub-ps-pulses (100 fs, 1 kHz) that can be tuned all over the VIS and NIR spectral range. We find two distinct efficiency maxima in the VIS and NIR spectral range and a pronounced dependence on the light polarization. Our findings are discussed within two excitation mechanisms: (1) The spatial modulation of the NIR recording pattern is imprinted onto the homogeneous gate light distribution via a one-photon-absorption process. (2) The photon energies of recording and gating light add-up via a two-photon process. Despite these new paths for carrier excitation, the further development of the grating follows the steps of the well-known photorefractive process. Financial support (DFG INST 190/165-1 FUGG) is gratefully acknowledged.