Growth and characterization of rubidium titanyl phosphate thin films by pulsed laser deposition

Abstract

The mm2 orthorhombic potassium titanyl phosphate crystal, i.e. KTiOPO4 (KTP), is a famous biaxial nonlinear optical crystal widely used commercially for second harmonic generation (SHG) or optical parametric oscillation (OPO) pumped by a 1.064 μm Nd:YAG laser for example. Most of its applications are based on bulk single KTP crystals. However, there is a strong interest to elaborate submicrometric waveguides in the framework of integrated photonic device. Such waveguides could be a serious alternative to efficient low energy nonlinear optical devices in particular for Telecom or spectroscopic applications.PLD is a technique particularly well suited for growing single oxides films with complex chemical composition. This technique consists in a high energy laser ablation of a material with the same chemical composition than that of the desired layer. The plasma of the ablated material is then condensed on the substrate and heated to a temperature such as the aggregates can self-organize on the atomic lattice of the substrate leading to the epitaxial layer.In this study, we performed epitaxial growth of the RbTiOPO4 (RTP) phase on KTP single crystals by PLD. The target that has been used was a single RTP crystal. However, by chemical analysis and XRay diffraction we demonstrated that due to alkali interdiffusion between film and substrate, it was not possible to achieve a pure layer of RTP but most likely an mixed stoichiometry KxRb(1-x) TiOPO4 but still in epitaxy.