Hannover 2013 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 43: Poster II
Q 43.37: Poster
Wednesday, March 20, 2013, 16:00–18:30, Empore Lichthof
Two-photon absorption and nonlinear refractive index in nominally undoped, thermally reduced LiNbO3 — Holger Badorreck, •Stefan Nolte, Pia Baeune, and Mirco Imlau — School of Physics, Osnabrueck University, Germany
The two photon absorption coefficient β and the nonlinear index of refraction n2 are determined in nominally undoped, thermally reduced LiNbO3 single crystals by means of the z-scan technique. The crystals under investigation have become attractive for ultrafast photonics due to their unique photosensitive features over a huge timescale ranging from 100 fs to a few ms. It is well established that small bound NbLi4+ and NbLi4+:NbNb4+ polarons are at the origin of the photosensitivity and allow for visionary applications such as ultrafast holography (cf. e.g. M. Imlau et al. Opt. Express 19, 15322 (2011)). However, a non-neglectable impact of the small polaron density on the nonlinear electric susceptibility of third order can be expected, as well, that has not been studied, so far.
We present our results on nominally undoped LiNbO3 with thermal pre-treatment and compare our findings with untreated samples.
An increase of the nonlinear electric susceptibility is distinguishable and is discussed in the frame of band-edge shifts due to alterations in the crystals’ stoichiometry. We further discuss the impact of beam profile applied for the z-scan technique. Here, a spatial filtering with focusing mirrors has been realized to obtain a spatially trimmed Airy profile.
Financial support by the DFG (IM 37/5, INST 190/137-1) is gratefully acknowledged.