| 摘要 |
PURPOSE:To elevate the efficiency, by forming a crystal layer which has a higher refractive index than a substrate and generates double refraction, on the substrate, and providing a stripe-like area, so that propagation phase constants of an optical waveguide mode in which oscillating electric field components meet at right angles with each other are made to be in coincidence. CONSTITUTION:A waveguide layer 2 is provided by forming a crystal layer whose refractive index is higher than that of a crystal substrate, for instance, a crystal film such as an iron garnet (YIG) film, in thickness of about hundreds of A-several mum, by a liquid phase growth method, etc., on the substrate of a garnet (GGG) single crystal 1, and an optical waveguide part 3 patterned by a fine working technique is formed. When equivalent refractive indexes against a TE wave and a TM wave in the plane waveguide having thickness t1 of the waveguide part 3 and thickness t2 of the part except the waveguide part are denoted as n1', n1 and n2', n2, equivalent refractive indexes nTE, nTM of TE and TM waves propagating in the waveguide part 3 are varied together with width W of the waveguide part 3 as shown in the figure, become as nTE= nTM at the time of width WO, and the equivalent refractive indexes become equal. In this way, a mode converting element which is small-sized and has good efficiency is formed. |
