Aravazhi, S.

Geskus, D.

Pollnau, Markus

English

Rare-earth-ion-doped $KY(WO_4)_2 (KYW)$ is an important candidate for solid-state lasers. Its high refractive indices of the order of 2.0 make it attractive also for applications as integrated optical devices. Liquid phase epitaxy was employed for growing mono-crystalline KYW thin films co-doped with $Yb^{3+}$, $Lu^{3+}$, and $Gd^{3+}$. Concentrations of the optically inert co-dopants $Lu^{3+}$ and $Gd^{3+}$, which decrease or increase the KYW lattice parameters, respectively, were optimized for lattice matching with the KYW substrate. $Lu^{3+}$ was partially replaced by $Yb^{3+}$ to achieve active optical doping from a few up to 20%. Optimized growth conditions provided crack-free layers

University of Twente Research Information

Growth of Yb3+, Lu3+, Gd3+ co-doped KY(WO4)2 thin layers  S. Aravazhi, D. Geskus, K. Wörhoff, and M. Pollnau  Integrated Optical MicroSystems Group, MESA+ Institute for Nanotechnology, University of Twente P.O. Box 217, 7500 AE Enschede, The Netherlands phone: +31-53-4892796, e-mail: s.aravazhi@ewi.utwente.nl Rare-earth-ion-doped KY(WO4)2 (KYW) is an important candidate for solid-state lasers. Its high refractive indices of the order of 2.0 make it attractive also for applications as integrated optical devices. Liquid phase epitaxy was employed for growing mono-crystalline KYW thin films co-doped with Yb3+, Lu3+, and Gd3+. Concentrations of the optically inert co-dopants Lu3+ and Gd3+, which decrease or increase the KYW lattice parameters, respectively, were optimized for lattice matching with the KYW substrate. Lu3+ was partially replaced by Yb3+ to achieve active optical doping from a few up to 20%. Optimized growth conditions provided crack-free layers.   Introduction  Due to its high refractive index of the order of 2.0, good thermal conductivity, and the possibility of doping with different rare-earth ions, monoclinic KY(WO4)2 (KYW) is a highly promising material for high-power solid-state lasers [1,2]. Doping with Yb3+ provides high absorption and emission cross sections [2]. In thin-film geometry, this material is also suitable for waveguide lasers [3]. Co-doping the layer with appropriate amounts of Lu3+ and Gd3+ resulted in KY(WO4)2:Yb (1.7 at%) thin films with increased refractive index contrast, thus reducing the required layer thickness for waveguiding, while simultaneously providing lattice matching between layer and substrate [4]. For thin-disk laser applications, highly Yb-doped KYW layers are needed. This can be achieved by either growing KLuW:Yb layers on KLuW substrates because of the similar ion radii of Yb and Lu [5] or co-doping a KYW:Yb layer with Gd for compensating the induced lattice mismatch with respect to the KYW substrate. In this paper, we report the liquid phase epitaxy (LPE) of crack-free KYW:Yb (2.4 mol%) layers co-doped with Lu and Gd and crack-free KYW:Yb (20 mol%) layers co-doped with Gd.  Experiment and Results  LPE with a vertical dipping method [3] was employed for the growth of layers onto pure KYW [010] substrates of size 1×1 cm2. The following compositions were grown in K2W2O7 solvents: KYb0.024Gd0.13Lu0.246Y0.6(WO4)2 and KYb0.20Gd0.13Y0.67(WO4)2. The incorporation of Yb and Lu ions induces tensile strain, while the incorporation of Gd ions leads to compressive strain [6], i.e., adjusted amounts of Yb and/or Lu ions, on the one hand, and Gd ions, on the other hand, can compensate each other [4]. Calculation of the lattice mismatch helped us to achieve layer growth with small lattice mismatch of f = 0.04625 %, as confirmed by X-ray diffraction measurements. The mono-crystallinity of the layers was achieved at a low supersaturations by slow growth rates. In this way, crack-free layers of KYW:Yb co-doped with Gd and Lu of thickness 3-5 µm and KYW:Yb codoped with Gd of thickness 30-40 µm were grown (Figs. 1a and b).  (a)  (b)   Fig. 1.  Crack-free co-doped crystals of (a) KYW:Yb (2.4 mol%), Lu (24.6 mol%), Gd (13 mol%) and (b) KY(WO4)2:Yb (20 mol%), Gd (13 mol%)  Conclusions  LPE was successfully employed for the growth of co-doped KYW layers. The concentrations of Yb, Lu, and Gd were optimized for lattice matching with the KYW substrate, leading to crack-free layers. 3-5 µm thick layers of KYW:Yb (2.4 mol%) co-doped with Gd and Lu and 30-40 µm thick layers of KYW:Yb (20 mol%) co-doped with Gd were grown. These results form a basis for the fabrication of KYW:Yb, Lu, Gd thin layers suitable for solid-state lasers and integrated optical devices.  Acknowledgment  This work was supported by the Netherlands Organisation for Scientific Research via a "Vici" personal research grant to M. Pollnau.  References  [1] N.V. Kuleshov, A.A. Lagatsky, V.G. Shcherbitsky, V.P. Mikhailov, E. Heumann, T. Jensen, A. Diening, and G. Huber, “CW laser performance of Yb and Er,Yb doped tungstates”, Appl. Phys. B 64, 409 (1997). [2] N.V. Kuleshov, A.A. Lagatsky, A.V. Podlipensky, V.P. Mikhailov, and G. Huber, “Pulsed laser operation of Yb-doped KY(WO4)2 and KGd(WO4)2”, Opt. Lett. 22, 1317 (1997). [3] Y.E. Romanyuk, C.N. Borca, M. Pollnau, S. Rivier, V. Petrov, and U. Griebner, “Yb-doped KY(WO4)2 planar waveguide laser”, Opt. Lett. 31, 53-55 (2006). [4] F. Gardillou, Y.E. Romanyuk, C.N. Borca, R.P. Salathé, and M. Pollnau, “Lu, Gd co-doped KY(WO4)2:Yb epitaxial layers: Towards integrated optics based on KY(WO4)2”, Opt. Lett. 32, 488-490 (2007). [5] S. Rivier, X. Mateos, O. Silvestre, V. Petrov, U. Griebner, M.C. Pujol, M. Aguilo, F. Diaz, S. Vernay, and D. Rytz, “Thin-disk Yb:KLu(WO4)2 laser with single-pass pumping”, Opt. Lett. 33, 735-737 (2008). [6] K.H. Hellwege and A.M. Hellwege, eds., Numerical Data and Functional Relationships in Science And Technology, Landolt-Börnstein Series III/7, Part f (Springer-Verlag, 1977).  

Growth of Yb3+, Lu3+, Gd3+ co-doped KY(WO4)2 thin layers

https://ris.utwente.nl/ws/files/5394161/Aravazhi_S._IEEE_LEOS_Benelux_Ch._Nov_08_Pp._219-220_Enschede.pdf

Growth of Yb<sup>3+</sup>, Lu<sup>3+</sup>, Gd<sup>3+</sup> co-doped KY(WO<sub>4</sub>)<sub>2</sub> thin layers

Abstract

Similar works

Full text

Available Versions

University of Twente Research Information