a Institut für Angewandte Physik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, D-07743 Jena, Germany
b Institut für Physikalische Hochtechnologie, Winzerlaer Straße 10, D-07745 Jena, Germany
Abstract:
We report on epitaxial {1 0 0} K1−xRbxTiOPO4 waveguide films for the visible spectral range grown on KTiOPO4 substrates by liquid phase epitaxy. Using the m-line technique a refractive index increase of Δnx≈0.007 and Δnz≈0.004 for TM and TE polarisation has been determined for a K0.78Rb0.22TiOPO4 film. Optical transmission and nearfield distribution are comparable to conventional ion-exchanged waveguides. Typical attenuation of about 1 dB/cm for both TM and TE polarisation was obtained at λ=532 and 1064 nm. Energy-dispersive X-ray spectrometry reveals solid-solution films with graded rubidium composition profiles. X-ray rocking curve analyses confirm the epitaxial growth process and indicate perfect and relaxed K1−xRbxTiOPO4 films. Atomic force microscopy investigations reveal regular step structures with step heights Δh<1.3 nm resulting in rms-roughness values of ≈0.4 nm.