Fabrication-Tolerant O-Band WDM Filter With Phase-Balanced Tapered Arms and Wavelength-Independent Couplers

We design, simulate, and experimentally demonstrate a coarse wavelength-division de-multiplexing system based on cascaded Mach-Zehnder interferometers (MZIs) operating in the O-band. The fabricated devices are built on a monolithic silicon photonics platform in a state-of-the-art CMOS foundry. The fabrication tolerance of the device was obtained by a combination of analytical and 3D Finite-difference time-domain (FDTD) methods. Fabrication-tolerant wavelength-independent couplers were used in order to achieve broadband splitting ratios (SRs) and ensure device stability along the entire wavelength range. In addition, phase-balanced linear tapers were used to allow for arbitrary waveguide width values for the MZIs. Experimental results show very high-performance stability across different wafer test sites with a mean channel spectral shift of only 1.03 nm and a total device footprint of 0.582 mm $^{2}$ .