| 摘要 |
PURPOSE:To eliminate the need for an optical waveguide which has a small radius of curvature and to make the length of a thin film heater sufficiently long as a phase shifter by providing a Mach-Zehnder type optical interferometer circuit which has a specific optical path length difference in the middle of a ring-shaped optical waveguide. CONSTITUTION:The ring-shaped optical waveguide 2 which constitutes a closed loop is arranged in a clad layer on a silicon substrate 1 and coupled with input and output optical waveguides 13a and 13b through directional couplers 12 and 12b respectively. Then, the asymmetrical Mach-Zehnder optical interferometer circuit 11 which has a resonance frequency interval in C/n.l (C: light velocity, n: refractive index of optical waveguide) and the peripheral length l of the ring-shaped optical waveguide 2 is inserted into the ring-shaped optical waveguide 2. Namely, the interferometer circuit 11 is constituted by coupling the directional couplers 12a and 12b by the two optical waveguides 13a and 13b which are l different in length. Consequently, the need for an optical waveguide which has an extremely small radius of curvature is eliminated and the phase shifter is made sufficiently long. |
