Growth and optical properties of Nd:LaVO 4 monoclinic crystal
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Huaijin Zhang,a) Haohai Yu, Honghao Xu, Hengjiang Cong, and Jiyang Wang State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100, China (Received 21 March 2012; accepted 24 July 2012)
Nd-doped LaVO4 crystals with the concentration up to 0.94 at.% were successfully grown by the Czochralski method. X-ray powder diffraction measurement reveals that this crystal belongs to a monoclinic space group P21/n. Refractive indices of Nd:LaVO4 have been measured with two right angle prisms for the first time to our knowledge and show that they are anisotropic. Its absorption and fluorescence spectra are also investigated. With the Judd–Ofelt theory, the optical parameters calculated are X2 5 2.142 1020 cm2, X4 5 3.704 1020 cm2, and X6 5 2.948 1020 cm2. By these parameters, the absorption oscillator strengths, line strengths, transition probabilities, fluorescence branch ratios, radiative lifetime, and integrated emission cross section are also derived and compared with familiar vanadates, which show that Nd:LaVO4 is a atypical material and has potential applications in the lasers, especially in the pulsed lasers. I. INTRODUCTION
Rare-earth (RE) orthovanadate compounds (where RE is a lanthanide series ion including both Sc and Y ions) have wide applications as catalysts, polarizers, laser host materials, and phosphors.1–4 When doped with RE ions such as Nd, Yb, or Tm, this series of crystals have been identified to be excellent laser materials. Nowadays, Nd-doped YVO4, GdVO4, and LuVO4 are three kinds of commercial vanadates, which possess large absorption and emission cross sections, wide absorption and emission spectra, and large thermal properties,5–9 attracting attention to study novel vanadate laser materials. Generally, with increasing ionic radius, RE31 ions show a strong tendency toward monazite-structured orthovanadate due to its higher oxygen coordination number of 9 as compared with 8 of the zircon.10 Therefore, lanthanum orthovanadate (LaVO4) possesses monoclinic structure, which is different with the structures of YVO4, GdVO4, and LuVO4. Due to the low symmetry of LaVO4, it is difficult to grow the crystal with fixed orientation and study its anisotropy of properties. Up to now, the Nd- and Yb-doped LaVO4 have been reported including growth, optical properties, and laser performance with a Ti:sapphire as a pump source with unknown directions.11–13 However, for a crystal, its structural anisotropy is an intrinsic characteristic and a determinate factor for its physical properties. As a laser crystal, the anisotropy of refractive indices and spectra including absorption and emission spectra determines its laser a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.290 2528
J. Mater. Res., Vol. 27, No. 19, Oct 14, 2012
http://journals.cambridge.org
Downloaded: 22 May 2014
performance and application. However, to the best of our knowledge, no investigation on the Nd:LaVO4 has been reported about the anisotropy of r
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