Crystal growth and characterization of RbTi1−x−yYbxNbyOPO4/RbTiOPO4 (001) non-linear optical epitaxial layers

Abstract

In this paper we report the growth of RbTi_1−x−yYb_xNb_yOPO₄/RbTiOPO₄ epitaxial layers by the liquid phase epitaxy method and discuss their structural and optical characterization. The layers were grown on (001) oriented substrates because this plane contains the phase-matching direction for Yb³⁺ type-II second-harmonic generation. In RbTi_0.971Yb_0.015Nb_0.014OPO₄/RbTiOPO₄ epitaxial layers we obtained enough contrast of refractive indices (Δn_z = 0.007 at 632.8 nm) to guide the light in TM polarization. The maximum Yb³⁺ concentration obtained in these layers was 1.43 × 10²⁰ atoms per cm³, which may be suitable for laser action. The lattice mismatch between the epitaxial layers and the substrates was low enough to obtain high quality epitaxial layers. Confinement of the light at 532 and 632.8 nm was demonstrated and there was good agreement between theoretical calculations, dark-mode spectra and modes of propagation.