Photonic junction based on dark spatial solitons

We present a fundamental study on the capability of a crossing of two optical waveguides based on dark-spatial solitons to act as a controllable optical beam splitter. Our study is based on the fact that the guided beam is diffracted at the waveguide crossing by an effective phase screen formed by the soliton collision profile. We find that when each dark soliton is immersed into its own bright background, the corresponding optical junction can not operate. This is because the finite width of the backgrounds acts as a low-pass filter over the diffracted beam, and because the onset of the cross-phase modulation instability effect occurs for small enough collision angles.