Ultraviolet patterning of KTiOPO 4 thin films through metallo-organics
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Ultraviolet patterning of KTiOPO4 thin films through metallo-organics Ken-ichi Noda, Wataru Sakamoto, Toshinobu Yogo, and Shin-ichi Hirano Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan (Received 15 October 1997; accepted 9 April 1998)
Patterned KTiOPO4 (KTP) films were successfully synthesized through metallo-organics using ultraviolet (uv) patterning. A homogeneous precursor solution was prepared by the reaction control of (n BuO)2 P(O) (OH), Ti(OEt)4 , and KOEt in ethanol. The solubility of the KTP precursor films in ethanol changed with uv irradiation because of the polymerization of KTP precursor. The patterned KTP precursor films crystallized to single-phase KTP after heat treatment at 600 ±C for 2 h. The patterned films were found to be exactly stoichiometric KTP.
I. INTRODUCTION
Second harmonic generation (SHG) of infrared laser through a nonlinear optical material is one of the most effective methods to generate blue-green laser. Potassium titanyl phosphate (KTiOPO4 : KTP) single crystal has been used in application for SHG materials because of its remarkable nonlinear optical characteristics, such as higher nonlinear optical coefficients, wide acceptance angles, thermally stable phase-matching properties, and high optical damage threshold.1–3 Confinement of the interacting waves to a guiding structure of nonlinear optical crystal greatly increases the SHG efficiency, and the quasi-phase-matching (QPM) using a segmented waveguide has been expected for an application to high-efficient SHG system.4 – 8 In addition, optical waveguide devices have also been receiving great attention in electro-optic applications for integrated optics, such as wave mixing, intensity phase modulation, and high-speed switching. KTP is an effective material for not only nonlinear optical but also electro-optic devices, because of its low photorefractive effect, large linear electro-optic coefficients, and low dielectric constants.3,9,10 Therefore, the KTP waveguides have been promised in both nonlinear optical and electro-optic devices. Waveguides of KTP single crystals mainly have been fabricated using rubidium ion-exchange processing in a mixture of RbNO3 and Ba(NO3 )2 , since KTP shows highly anisotropic ion-exchange behavior along the c-axis.2–8 Cesium or thallium is sometimes used as an ion-exchange element instead of rubidium. Recently, thin films of KTP and its isomorphs, which could be used as planar waveguides, have been fabricated on various substrates by several methods, including sol-gel method,11–14 laser ablation technique,15,16 and liquid phase epitaxy (LPE).17 KTP fiber synthesis by the sol-gel method was also reported.18 222
J. Mater. Res., Vol. 14, No. 1, Jan 1999
The sol-gel method especially has advantages of synthesizing high purity materials at low processing temperature, feasible composition control, good homogeneity, and versatile shaping. Hirano et al. reported the synthesis o
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