Abstract: The invention relates to a fabrication of an integrated optical isolator using a Multi-Mode Interference (MMI) structure and a cladding layer comprising magneto-optical material, which remove needless reflection generated in the course of light propagation and make short length integration possible. Thus, the invention uses nonreciprocal phase shift effect that optical characteristics are altered according to the direction of light propagation. In order to fabricate a light waveguide optical isolator, an input light should be separated into two light waveguides having the same power. That is, for the purpose of reducing the length of optical isolator device, the waveguide length needed to separate an input light into two light waveguides should be shortened. Since the light waveguide length of MMI structure is much shorter than the length of Mach-Zehnder light waveguide for separating an input light into two waveguides, the length of optical isolator device using MMI structure can be reduced.

Abstract: A semiconductor magneto-optical integrated optical isolator is realized with a Mach-Zehnder integrated optical isolator in which a cladding and a guiding layer of light waveguide are composed of magnetic material. Here, it uses nonreciprocal phase shift created when light propagation direction is changed. The fundamental element deriving this nonreciprocal phase shift is the Faraday rotation of magnetic material. Therefore, it is essential to have large Faraday rotation in order to fabricate a short length integrated optical isolator. However, since magnetic material of bulk state does not have large Faraday rotation, there need the length of several mm units for fabricating an isolator. The invention is to realize an integrated optical isolator using magneto-optical crystal in which magneto-optical material and dielectric substance have periodic structure.