| 摘要 |
PURPOSE:To make the characteristics as a light modulator close to those of waveguide having many single modes and propagating only several modes, by increasing the light intensity density while making use of the merits of the multimode waveguide. CONSTITUTION:As an optical guide, LiTaO3 single crystal 1 of multimode waveguide is used, and the section thereof has a continuously changing curvature radius, namely smaller in curvature radius in the vicinity of the entry and exit ends of multimode fibers 3 and 5, and larger in curvature radius in the central part mounting a stripe-formed electrode 2 of Cr-Al. Both ends of this single crystal are polished so as to directly coupled with the fibers. When the applied voltage to this modulator is decreased, it becomes close to a two-dimensional waveguide, so that the quantity of light transmitted to the fiber 5 may be reduced. This effect is found only in the TE mode, and the TM mode is cut by means of a thin film polarizing element 4. |
