Near-athermal silicon nitride 4-channel O-band (de)multiplexer with ~2 pm/K temperature sensitivity

We demonstrate a 4-channel O-band (de)multiplexer based on silicon nitride (SiN) Mach-Zehnder interferometer (MZI) lattice filters. By utilizing geometry-dependent modal behavior to tailor the effective thermo-optic coefficient (dn_eff/dT) of the SiN waveguides, near-athermal operation is achieved against global temperature fluctuations. The device architecture utilizes Hermite-curve-assisted folded arms to ensure a compact footprint while maintaining high sensitivity to local micro-heaters for power-efficient channel alignment. Fabricated on an 8-inch wafer with 300-nm-thick SiN, the device exhibits a significantly suppressed temperature sensitivity of ~2 pm/K. The integrated phase shifters achieve a low π-phase-shift power of ~30 mW. Comparative analysis with state-of-the-art SiN platforms highlights the superior performance of this design in both passive thermal stability and active tuning efficiency.