Broadband in-plane light bending with a doublet silicon nanopost array

The in-plane tailoring of light propagation is significant in on-chip optical interconnections. Recently, an in-plane negative-angle refraction was realized with a thin line of silicon nanoposts, which are at resonance in the first angular momentum channel. This advancement is different from metasurface research, which mostly focuses on out-of-plane operations. In this paper, we experimentally demonstrate that a thin array of doublet silicon nanoposts, in which each unit comprises two tangent nanoposts functioning as an upright interface, remarkably improve efficiency for molding light. The designed upright interface exhibits a broadband response featuring high efficiency in a negative-angle light bending in the wavelength of 1480-1600 nm. The broadband, compactness, low loss, and complementary metal-oxide semiconductor (CMOS) compatibility enable the use of the subwavelength array as an alternative component for on-chip optical control.