Unraveling the ultra-broadband beam splitter based on parallel coupled waveguides

Abstract An ultra-broadband beam splitter is theoretically realized using a directional parallel-cascaded coupled-waveguide structure, which is designed and investigated with the effective medium method and finite-difference time-domain method. The 1 dB bandwidth is 285 nm which is ranging from 1418 nm to 1703 nm, thereby covering the optical window for long-haul communication. The electric field distributions show that there is a recoupling zone and thereby resulting in the ultra-broadband operation. The proposed beam splitter can be naturally integrated into the silicon photonic integrated circuits, thereby facilitating the applications of silicon-on-insulator waveguides.