Reduction of the crosstalk between adjacent photonic components has been regarded as one of the most effective, yet most challenging approaches for increasing the packing density of photonic integrated circuits. Recently, extensive efforts have been devoted to this field, leading to a number of elaborate designs, such as waveguide supperlattice and nanophotonic cloaking, among others. Here we develop a simple and efficient crosstalk reduction approach for silicon-based nanophotonic circuits by introducing a periodic array of silicon strips between adjacent waveguides. Studies indicate that the coupling lengths can be extended by more than two orders of magnitude for a waveguide pair with an edge-to-edge distance of ~λ/3 at the telecommunication wavelength. Further investigations reveal that our method is effective for both strongly and weakly confined silicon photonic modes, and works well over a broad band of operational wavelengths. In addition, the crosstalk reduction technique is shown to be capable of improving the coupling lengths of other elements as well, such as vertical silicon slot waveguides. Our approach offers a promising platform for creating ultra-compact functional components that is fabrication friendly, thereby providing a feasible route toward the realization of photonic integrated circuits with ultra-high packing densities.
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