Magneto-optical garnets are attractive because of their high Faraday rotation and low optical loss in the near infrared. Therefore their use is generally in nonreciprocal devices, i.e., as optical isolators in optical communication. In this paper we present data concerning the deposition of Bi3Fe5O12 (BIG) thin films on (100) and (111) Gd3Ga5O12 substrates using pulsed-laser deposition. Laser-induced processes on the surface of the oxide target used for ablation were analyzed and numerous films were deposited. We found the BIG film quality to be strongly affected by oxygen pressure, laser energy density, and the Bi∕Fe film ratio, whereas temperature had a minor influence. We also investigated the BIG-film deposition using a target pressed from metallic Bi and Fe powders and found information on the growth behavior of BIG. We report on details of the film deposition and film properties determined by environmental scanning electron microscopy, energy dispersive x-ray analysis, Rutherford backscattering spectroscopy, and x-ray diffraction. In addition, we determined the Faraday rotation of the films.

One of the efforts of integrated optics is the integration of macroscopic optical components such as an optical isolator on a single chip. Therefore magneto‐optically active materials with high Faraday rotations are needed. Bismuth iron garnet (BIG) Bi3Fe5O12 is known for its high Faraday rotation at room temperature, but it forms in a non‐thermodynamic way and only grows on garnet substrates like gadolinium gallium garnet (GGG) Gd3Ga5O12. Our ambition was to investigate the possibility of depositing such an integrated optical device based on magneto‐optical BIG. A general overview of our extensive fundamental research is given in this paper. We first analysed the growth mechanisms of BIG on GGG, especially the nucleation process and the film growth which are important for BIG film synthesis. Then we worked on a garnet buffer system to enable film formation on other substrate materials like silicon or fused silica. To obtain the optical constants of the deposited material, a fitting algorithm was implemented. It calculates the optical properties of material stacks from transmission measurements. Furthermore, we wanted to vary the lattice constants of the garnets for a better adaption to the substrates. Because different rare earth elements have different atomic radii, it should be possible to vary the lattice constant by incorporating these atoms in the crystal. Therefore a number of rare earth doped garnets were produced and their film properties were analysed. During the buffer development we found an oscillatory effect in the Faraday rotation, which was examined in detail.

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It is shown that the critical currents of high-Tc superconducting tapes fabricated by the coated conductor technologies are enhanced considerably if grain arrangements with large effective grain boundary areas are used. Increasing the aspect ratios of the grains reduces the deleterious effects of the grain boundaries. A practical road to competitive high-Tc cables is proposed.