Compact wavelength-insensitive fabrication-tolerant silicon-on-insulator beam splitter

A star coupler-based beam splitter for rib waveguides is reported. A design method is presented and applied in the case of silicon-on-insulator rib waveguides. Experimental results are in good agreement with simulations. Excess loss lower than $1\mathrm{dB}$ is experimentally obtained for star coupler lengths from 0.5 to $1\mathrm{\mu m}$. Output balance is better than $1\mathrm{dB}$, which is the measurement accuracy, and broadband transmission is obtained over $90\mathrm{nm}$.