Compact and high-efficient wavelength demultiplexing coupler based on high-index dielectric nanoantennas

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 SiO_2 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.     

塔里木河中游植物群落生活型谱的特点

塔里木河中游植物群落生活型谱组成中,地面芽植物和一年生植物占主要地位,分别为41％和32％。反映这一地区的植被受温带荒漠气候支配。