Inversely Designed 1 × 4 Power Splitter with Arbitrary Ratios at 2-μm Spectral Band

We demonstrate integrated 1 × 4 power splitters at 2-μm spectral range with arbitrary power-splitting ratios. The devices are based on digital meta-structures that are designed by algorithm. Four devices with split ratios of 1:1:1:1, 2:2:1:1, 2:2:2:1, and 4:3:2:1 are inversely designed to conceptually prove the capability of arbitrary split ratios. Up to four design objectives including both efficiency and power ratios between the four outputs of each device have been jointly optimized. The total transmission efficiencies of all the algorithm-optimized splitters are above 80%, which is predicted by simulations. The power ratios are well consistent with the design targets as well. Then, the devices are fabricated on silicon-on-insulator platform with the device footprint of only 3.6 μm × 3.6 μm. The fabricated splitters are characterized at wavelength range from 1945 to 1975 nm. The total transmission efficiencies of all the splitters are measured to be higher than 70%, and the power ratios agree with the simulation results.