A new type optical circulator has been proposed, using a nonreciprocal magneto-optic directional coupler whose two waveguides with different widths are arranged in the same plane. It can be fabricated more easily than previous nonreciprocal waveguide devices.

We report Ultraviolet (UV)-induced visible light luminescence in artificial-lattice thin films of ion-doped silica glass (silica superstructure thin films). The film was composed of periodic nanometer layers of germanium-doped silica (Ge:SiO2), titanium-doped silica (Ti:SiO2), and tin-doped silica (Sn:SiO2). The thickness of each layer was between 10 and 30 nm. Despite the small thickness of the film (few microns), a relatively bright luminescence of white light was observed, along with cathode-ray luminescence in the superstructure film. In addition, irradiation of the superstructure film with UV light led to light amplification by stimulated emission at 405 nm. The experimental results suggest the potential application of silica superstructure thin films as optical amplifiers.