Compact and high-efficient wavelength demultiplexing coupler based on high-index dielectric nanoantennas**Project supported by the National Key Research and Development Program of China (Grant Nos. 2017YFA0205700 and 2015CB932403) and the National Natural Science Foundation of China (Grant Nos. 11174062, 51472057, and 21790364).

Abstract

Wavelength demultiplexing waveguide couplers have important applications in integrated nanophotonic devices. Two of the most important indicators of the quality of a wavelength demultiplexing coupler are coupling efficiency and splitting ratio. In this study, we utilize two asymmetric high-index dielectric nanoantennas directly positioned on top of a silicon-on insulator waveguide to realize a compact wavelength demultiplexing coupler in a communication band, which is based on the interference of the waveguide modes coupled by the two nanoantennas. We add a Au substrate for further increasing the coupling efficiency. This has constructive and destructive influences on the antenna’s in-coupling efficiency owing to the Fabry–Perot (FP) resonance in the SiO2 layer. Therefore, we can realize a wavelength demultiplexing coupler with compact size and high coupling efficiency. This coupler has widespread applications in the areas of wavelength filters, on-chip signal processing, and integrated nanophotonic circuits.