Refractive index change of multicomponent glass films for bismuthate erbium-doped waveguide amplifiers prepared by radio-frequency magnetron sputtering under different magnetic fields of cathode

• Published in: Surface & coatings technology Vol. 240; pp. 399 - 404
• Main Authors: Kageyama, Junichi, Yoshimoto, Mamoru, Matsuda, Akifumi, Kondo, Yuki, Ono, Motoshi, Sugimoto, Naoki
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.02.2014; Elsevier
• Subjects: Amplifiers; Applied sciences; Cladding; Cross-disciplinary physics: materials science; rheology; Deposition; Exact sciences and technology; Glass; Magnetic field; Magnetic fields; Magnetron sputtering; Materials science; Metals. Metallurgy; Multicomponent glass film; Physics; Production techniques; Refractive index; Refractive index control; Refractivity; RF magnetron sputtering; Surface treatment; Surface treatments; Waveguides; RF magnetron sputtering; Refractive index control; Multicomponent glass film; Magnetic field; Doping; Magnetic field effects; Surface treatments; Sputtering; Magnetrons; Rare earths; Physical vapor deposition; Waveguides; Magnetic fields; Radiofrequency sputtering; Cathodes
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2013.12.063

Bismuthate erbium (Er)-doped waveguide amplifiers consist of an Er-doped core surrounded by an Er-free cladding film with lower refractive index. The propagation loss of a waveguide critically depends on both the thickness and the refractive index of its core and cladding films; hence, these two properties of such films must be controlled. We studied the influence of magnetic fields on a batch-to-batch variation of the refractive index of Er-free multicomponent cladding glass films deposited by radio-frequency magnetron sputtering. We successfully controlled the variation in the refractive indices of the films to within 0.001 throughout the lifetime of the target by applying the design techniques of a weak magnetic field and flat magnetic field lines to a magnetic array for sputtering. We also found that the self-bias voltage maintained a high value irrespective of target consumption. This phenomenon is thought to be related to stabilization of the deposition rate and the refractive index of the films under the experimental sputtering conditions. •7μm-thick glass films with controlled index are deposited by RF magnetron sputtering.•Effect of magnetic field on the refractive index variation of the films is examined.•Improved magnetic array controls the batch-to-batch variation of index within 0.001.•Index variations derive from O content change in the film as deposition rates slow.•The deposition rate depends on the self-bias voltage linked with magnetic field.