On-chip silicon photonic nanohole metamaterials enabled high-density waveguide arrays.

High-density silicon waveguide arrays manufactured on a complementary metal-oxide-semiconductor (CMOS)-foundry platform hold great promise for optical information processing and photonic integration. However, evanescent waves arising from nanoscale confinement would cause significant optical crosstalk in waveguide arrays, which remains a vital issue in various applications. Here, by utilizing silicon photonic nanohole metamaterials, we propose a scheme to greatly suppress the crosstalk in the devices and then demonstrate ultra-compact low-crosstalk waveguide arrays. For a 100-µm-long waveguide array at a half-wavelength pitch, low crosstalk of -19 dB can be obtained in a wide range of wavelengths (1500 nm-1580 nm). In the experimental demonstrations, our approach exhibits the ability to suppress the crosstalk over a broad bandwidth without substantially increasing the propagation loss as well as the promising design flexibility, which shall pave the way for metamaterials enabled high-density waveguide arrays.