$C$ -Band Optical 90$^{\circ}$ Hybrids in Silicon Nanowaveguide Technology

We present a fully passive silicon nanowire-based optical 90° hybrid based on a 4 × 4 multimode interference (MMI) coupler for application in coherent receivers. Simulations show 4×4 MMI coupler performance regarding excess loss, imbalance, bandwidth, and phase accuracy. The 4×4 MMI couplers show stable performance over C-band with excess loss and imbalance<; 0.5 dB and phase accuracy better than 5°. We obtain over C-band minimum extinction ratios of 20 dB.