Emission characteristics, crystalline phase and composition of vapor-transport-equilibrated Er:LiNbO3 crystal codoped with 6 mol% MgO
✍ Scribed by De-Long Zhang; Bei Chen; Hong-Li Liu; Yu-Ming Cui; E.Y.B. Pun
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 733 KB
- Volume
- 255
- Category
- Article
- ISSN
- 0169-4332
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✦ Synopsis
From the viewpoint of integrated optics, the photorefractive effect of LiNbO 3 crystal is undesired, and this detrimental effect definitely limits the applications of this material in this field. It is well known that doping with above 4.6 mol% MgO into a congruent ([Li]/[Nb] % 94%) crystal allows to substantially improve the resistance to the photorefractive damage . However, a large amount of MgO doping causes difficulty in growing Er/Mgcodoped crystal of high optical-quality. Near-stoichiometric (NS) MgO-doped LiNbO 3 is a promising substrate material for the fabrication of photorefractive-damage-resistant Ti:LiNbO 3 waveguide devices. This is because the NS LiNbO 3 needs less amount of MgO (>0.2 mol%) to prevent photorefractive damage . The lower doping level of MgO makes it possible to grow high opticalquality Er/Mg-codoped single crystal. In addition, the NS Mg-doped LiNbO 3 crystal also retains the inherent advantages of a pure NS crystal over the congruent material such as: (i) lower extraordinary refractive index, which is favorable for the waveguide application; (ii) larger electro-optic effects [5]; (iii) remarkably lowered coercive field strength needed for ferroelectric domain reversal [6,7]; (iv) higher resistance to thermochemical reduction; (v) absence of inhomogeneous broadening in optical, electron paramagnetic resonance and other spectroscopic measurements. Moreover, the as-grown near-stoichiometric crystal is single-domain and there is no need for repoling. In our earlier paper, optical absorption characteristics in bulk Er (0.4 mol%)/Mg (6 mol%)-codoped NS LiNbO 3 crystals, prepared by vapor-transport-equilibration (VTE), have been reported . In this article, we report visible (downconversion and 980-nmupconversion) and near-infrared emission characteristics of these VTE crystals. The crystalline phases contained in these VTE crystals are determined by comparing the infrared emission characteristics of these crystals with those of a Z-cut only Er (2.0 mol%)-doped VTE LiNbO 3 crystal and three X-cut Er:MgO (4.5 mol%):LiNbO 3 crystals prepared by standard local Er-doping followed by VTE treatment. The concentrations of the constituent elements including Li, Nb, Mg and Er in these VTE crystals were determined by atomic absorption spectroscopy and neutron activation analysis.