Subwavelength structures for nanophotonic couplers, colourless splitters, polarization control and mid-infrared waveguides

We report our recent advances in development of subwavelength engineered dielectric metamaterial structures for integrated photonics. By locally engineering the refractive index of silicon by forming a pattern of holes at the subwavelength scale it is possible to manipulate the flow of light in silicon nanophotonic waveguides [1], [2], [3], [4], [5], [6]. Specifically, we present a broadband fibre-chip edge coupler with a coupling efficiency exceeding 90% for direct coupling between cleaved SMF-28 optical fibres and silicon nanophotonic waveguides [7], as well as the first implementation of a subwavelength nanostructure for laser-to-SOI chip coupling experiments with an InGaAsP/InP buried heterostructure laser. Furthermore, we report on dispersion engineered colourless multimode interference coupler operating over an ultra-broad wavelength range 1260 nm – 1675 nm, exceeding the O, E, S, C, L and U optical communication bands. We also present an integrated polarization controller with largely relaxed fabrication tolerances and tuneable over the complete C-band, with a measured polarization extinction range of 40 dB [8]. Implementations of subwavelength grating engineered structures for evanescent field sensing and mid-infrared silicon photonic circuits [9] with waveguide propagation losses < 0.9 dB/cm at 3.88 µm will also be discussed.