| 摘要 |
PURPOSE:To produce Fresnel lenses of thin films having high performance in large quantities at a low cost by providing the regions where the density of a diffusing material is nonuniform in a substrate plane near the surface of a dielectric substrate at the nonuniform thicknesses of the diffusing material in the substrate surface then subjecting the same to a diffusion treatment. CONSTITUTION:A metallic titanium film 2 is provided over the entire surface of a dielectric substrate 1 of a Z-axis single crystal of lithium niobate or the like. Films 3 of titanium are further formed like islands thereon by a photomask having the shapes of Fresnel zones and a lithographic method. The substrate is heated for about 5hr at about 1,000 deg.C in oxygen or air to diffuse Ti in the substrate 1 and to form a high refraction layer near the substrate surface, whereby a thin film optical circuit having the Fresnel lens of the thin film is obtd. It is possible to increase the optical utilizing rate of focusing light 5 by forming the patterns of the Ti on the substrate continuously as shown in the another figure. |
