N-rich silicon nitride angled MMI for coarse wavelength division (de)multiplexing in the O-band.

We report the design and fabrication of a compact angled multimode interferometer (AMMI) on a 600 nm thick N-rich silicon nitride platform (n=1.92) optimized to match the International Telecommunication Union coarse wavelength division (de)multiplexing standard in the O telecommunication band. The demonstrated device exhibited a good spectral response with Δλ=20  nm, BW3 dB ∼11  nm, IL<1.5  dB, and XT∼20  dB. Additionally, it showed a high tolerance to dimensional errors <120  pm/nm and low sensitivity to temperature variations <20  pm/°C, respectively. This device had a footprint of 0.02  mm×1.7  mm with the advantage of a simple design and a back-end-of-line compatible fabrication process that enables multilayer integration schemes due to its processing temperature <400°C.