Slot-waveguide-assisted temperature-independent Mach–Zehnder interferometer based optical filter

A new design of temperature-independent Mach–Zehnder interferometer (MZI) based optical filter involving a combined use of silicon (Si) wire waveguides and slot waveguides is presented. The ratio of the path-length difference for the two types of waveguides is introduced to tune the thermal performance of the filtering wavelength. This ratio and its derived parameters render a high-level of flexibility for optimizing the design of interferometers based on optical path-length difference. By adjusting the path-length difference ratio for Si-wire waveguides and slot waveguides in the asymmetric arms of the MZI, an ideal temperature-independent optical filter can be obtained, while the modified interference order is enhanced. The proposed method is verified via a two-dimensional finite difference time domain simulation.