PURPOSE: To produce an optical waveguide, etc., having projecting parts in the periphery of ion diffused region without executing intricate stages by immersing the optical waveguide or flat plate microlens into an etchant contg. hydrofluoric acid.
CONSTITUTION: This process consists of a primary ion exchange treatment to diffuse univalent ions having an ion radius larger than the ion radius of alkaline ions from the limited parts of a glass substrate 10 contg. the univalent alkaline ions and a secondary ion exchange treatment to diffuse the univalent alkaline ions originally contained in this glass substrate 10 from the surface subjected to the ion exchange treatment of the substrate 10. In such a case, the optical waveguide substrate is immersed into the etchant contg. the hydrofluoric acid, by which the annular projecting parts 14 enclosing the waveguide 11 regions exposed on the substrate end faces 15 are formed around these regions. Difference is generated in the etching speeds between the outer part of the diffusion front (the boundary between the ion diffused region and the non-diffused region) and the other part when the substrate is immersed into such etchant.
SATO SHIRO
IKEDA MITSUAKI
NISHIZAWA KOICHI
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