Epitaxial grown K1-xRbxTiOPO4 films with extremely flat surfaces for waveguiding

We report on epitaxial {100} 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 Deltan(1) approximate to 0.007 and Deltan(z) approximate to 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 lambda = 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 Deltah < 1.3 nm resulting in rms-roughness values of <approximate to>0.4 nm. (C) 2001 Elsevier Science B.V. All rights reserved.