Robust broadband athermal 2 × 2 Mach-Zehnder interferometer with sub-wavelength grating adiabatic couplers

We report an all-silicon thermally insensitive (-1.5pm/^∘C) 2×2 Mach-Zehnder interferometer (MZI) over a spectral range from 1540 to 1620 nm. Additionally, the proposed MZI exhibits no imbalance in its extinction ratio with temperature. The broadband spectral range with minimal temperature sensitivity is achieved by slightly overcompensating the MZI design for temperature variations. At the same time, the uniformity in the extinction ratio is controlled using sub-wavelength grating adiabatic couplers for splitting and combining.