The pulsed laser deposition (PLD) technique is an excellent method to prepare single crystalline complex oxide thin films. We have successfully grown films for the use in HTS SQUID-devices as well as for thin film optical waveguides. The Josephson junction used in the HTS SQUIDs is formed by a step edge type gain boundary junction. The step preparation is a very critical process in the SQUID preparation to achieve reproducible low 1/f noise devices. We have established a new ion beam etching process to achieve clean and steep edges in LaAlO3 (100) substrates. The 1/f noise of SQUIDs prepared with the new method is drastically reduced. In the process of developing thin film electro-optical waveguide modulators we investigated the influence of different substrates on the optical and structural properties of epitaxial BaTiO3 thin films. These films are grown on MgO(1 0 0), MgAl2O4(1 0 0), SrTiO3(1 0 0) and MgO buffered Al2O3(1 (1) over bar 0 2) substrates. The waveguide losses and the refractive indices were measured with a prism coupling setup. The optical data are correlated to the results of Rutherford backscattering spectrometry/ion channeling (RBS/C), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The dielectric constant, the ferroelectric hysteresis loop and the transition temperature (ferroelectric to paraelectric state) of the BaTiO3 thin films are measured.