Abstract: A substrate for mounting optical components and electric circuit components thereon, comprising an insulating substrate on which an electric circuit is to be formed and a metallic portion on which optical components are to be fixed by welding. This construction may be reversed; that is, an insulated layer on which an electric circuit is to be formed may be provided on a metallic board on which optical components are to be fixed by welding. A device constituted using this substrate permits improvement of the frequency band characteristic and a long-term stabilization of optical coupling efficiency.

Abstract: A structure for mounting on a base plate an optical element having a cylindrical portion. A holder member having a flat bottom surface is rotatably mounted on the cylindrical portion of the optical element. The holder member is mounted on and secured to a support member having an inclined upper surface so that the flat bottom surface of the holder member contacts the inclined upper surface of the support member in a face-to-face manner. The support member is secured to the base plate.

Abstract: A dielectric thin film optical transmission device in which a dielectric substrate has formed thereon a dielectric thin film of a refractive index larger than that of the substrate and the dielectric thin film has formed thereon in a desired pattern a dielectric layer of a refractive index smaller than that of the dielectric thin film and in which the dielectric thin film underlying the dielectric layer chiefly serves as a light waveguide to transmit light therethrough.