Keywords:Optical Power Couplers, Nano-Pixel Structure, Inverse Design
One typical optical power coupler is the Y-branch waveguide that has an input waveguide and two output waveguides. Symmetric Y-branch 3-dB couplers (output power ratio 1:1) are wavelength-independent and have been studied to some extent in the past. In contrast, couplers with an asymmetric splitting ratio still have difficulties that are not easily addressed for practical applications. In the asymmetric Y-branch waveguides, the cross-section of the input waveguide is different from those of the output waveguides, so that it is difficult to realize optical mode-matching among the waveguides. This may cause a high coupling loss from the input waveguide to the output waveguides. Therefore, a coupler with an asymmetric splitting-power-ratio design, in addition to a compact footprint and low excess loss is urgently needed. In this work, we proposed 1:9 and 1:99 optical power couplers based on inverse designed nano-pixel. Both couplers occupy a compact area of 2.88 × 2.88 μm2 with a low excess loss of 0.68 (1:9) / 0.41 dB (1:99) and a wide wavelength operation range of 1500-1600 nm.