| 摘要 |
PURPOSE:To obtain a small-sized thin film element having a simple structure and equalizing the TE wave propagation phase constant to the TM wave propagation phase constant by specifying the composition of a mangeto-optical garnet crystal formed on a substrate and the thickness and width of a waveguide. CONSTITUTION:On a nonmagnetic garnet crystal substrate an optical waveguide 3 of a magnetoptical garnet crystal layer 2 having a refractive index higher than that of the substrate is formed to manufacture an optical circuit. In the circuit, the magnetooptical garnet crystal is provided with a composition represented by the formula Y3-xAxFe5O12 (where A is >=1 kind of ino selected from G, Tb and Eu ions, and 0.1<x<0.6), the thickness t1 of the waveguide 3 is make the propagation phase constant for optical waveguide made (TE wave) having an oscillating electric field component in the direction parallel to the substrate smaller than the propagation phase constant for optical waveguide mode (TM wave) having an oscillating electric field component in the direction perpendicular to the substrate, and the width W of the waveguide 3 is set so as to equalize the TE wave propagation phase constant to the TM wave propagation phase constant. |
