Ultracompact splitter for submicrometer silicon-on-insulator rib waveguides

An ultracompact and efficient $1\times 2$ splitter for submicrometer silicon-on-insulator rib waveguides using a star coupler is reported. The structure proposed here is decidedly smaller than the usual splitters such as multi-mode interference or Y-branch devices and much less sensitive to technological fluctuations. Design of the compact splitter is optimized at $\mathrm{\lambda }=1.31 \mu \mathrm{m}$ with the effective-index method and a two-dimensional beam-propagation method. The excess losses are lower than 0.15 dB, and the dependence of the losses on wavelength between 1.23 and 1.63 μm is almost flat (variation less than 0.04 dB), which makes the device very interesting for coarse wavelength-division multiplexing applications within the silicon photonic technology.