High tolerant design of athermal Si wavelength filter using Mach–Zehnder interferometer

Abstract A design method for the athermal Mach–Zehnder wavelength filter, which is available in the Si-on-insulator platform, is proposed. We can obtain much higher fabrication-tolerant characteristics by introducing a condition, minimizing the dependence of the waveguide width on the athermal condition, to the wavelength filter design. Our design has the arm waveguides divided into four sections, and each section is appropriately designed to exploit athermal characteristics. We also reveal the relationship between the arm length (corresponding to the footprint) and the waveguide width (relating to the propagation loss) from the formularized equations for the wavelength filter design. One example of the Mach–Zehnder interferometer filter designed by the proposed method has lower spectral shift characteristics less than 1 pm K −1 entire C band even if the waveguide width errors occur, compared with the conventional design.