TEMPERATURE-INDEPENDENT AND ASYMMETRICALLY DIRECTIONAL COUPLER TYPE OPTICAL WAVEGUIDE WAVE-LENGTH FILTER

摘要

PROBLEM TO BE SOLVED: To prevent the change of central wavelength of a filter due to the ambient temp. change by mutually making the respective propagation constants of two optical waveguides equal in a desired central wave-length of the filter and the temp. coefficients of the respective equivalent refractive indices in the central wavelength of the filter. SOLUTION: Two flat plate optical waveguides composed of a core and a clad are formed on a Si substrate, an optical waveguide in the lower part uses an ARROW- B type waveguide 9 as an optical waveguide having small dispersion and the other optical waveguide in the upper part is an asymmetric four-layer flat plate waveguide 8 having a multilayered structure whose core is composed of two layers of a core 1 and a core 2. In the asymmetrically directional coupler type optical waveguide wavelength filter, the thicknesses dc1 , dc2 cores 1, 2 of the asymmetric four-layer flat plate waveguide 8 are set so as to make the respective propagation constants of the asymmetric four-layer flat plate wave-guide 8 and the ARROW-B type waveguide 9 equal and to make the temp. coefficients of equivalent refractive indices equal at the desired wavelength 1.55μm.