@Workshop{Supelec948,
author = {Ninel Kokanyan and David Chapron and Edvard Kokanyan and Marc Fontana},
title = {{Effect of Zr doping on the structure of Lithium Niobate crystals: Site spectroscopy and Chemometrics}},
year = {2016},
booktitle = {{NAMES\'16}},
month = {nov},
address = {Nancy (FRANCE)},
abstract = {At present, a strong limitation to the applications of LN
crystals comes from the fact that, under illumination with
visible or near-infrared light, there are semi-permanent
changes in the index of refraction of the crystal, due to the
photorefractive effect (or \" optical damage \"), causing beam
distortion and dramatically decreasing the device efficiency.
This drawbacks and limitation exist unless some strategy to
reduce the photorefractive effect is implemented [1]. The
resistance to optical damage can be increased considerably by
changing the LN crystal composition from congruent to
stoichiometric [2,3] and/or by adding to LN an appropriate
non-photorefractive dopant. Recently, different tetravalent
impurity ions (Hf 4+ , Zr 4+ , Sn 4+) were proposed as new
non-photorefractive impurity ions [4,5]. Complex
investigations of Hf as well as Zr doped congruent composition
LN crystals including photorefractive, non-linear optical,
compositional, electro-optical [6-9] properties have been
shown that tetravalent impurity ions with a threshold
concentration of around 2-3mol% can be considered as good
candidates for reduction of the photorefractive effect in LN
crystals with preserving of its main characteristics. In this
work the Zr doped LN crystals are investigated in order to
have a clear idea of the threshold concentration of the
impurity ion required for the reduction of the photorefractive
effect as well as sites occupied by different concentration Zr
ions in the structure of LN. Raman measurements were
investigated on Zr doped Lithium Niobate crystals with
different concentrations. Spectra were treated by fitting
procedure and Principal Component Analysis, which both provide
results consistent with each other (figure 1). The
concentration dependence of the frequency of main low-
frequency optical phonons give an insight of site
incorporation of Zr ions in the host lattice. The threshold
concentration of about 2% is evidenced, confirming that the
interest of Zr doping as an alternative to Mg doping for the
reduction of the optical damage in Lithium Niobate. These
results allow to explain the observed kink that we have found
in the EO behavior as function of [Zr] in LN:Zr doped crystals
[9]. Figure 1-The frequency of the mode E[TO 1 ] and the
scores of PC2 as a function on the concentration of Zr in LN
[1] T. R. Volk and M. Woehlecke.}
}