Arbitrary-direction, multichannel and ultra-compact power splitters by inverse design method

In this paper, we use the method of inverse design to theoretically design three 1 x 2 power splitters based on photonic-crystal-like (PhC-like) metamaterial structure by utilizing Lumerical FDTD solutions [https://www.lumerical.com/]. They have not only different output directions to meet the high development of photonic integrated circuits but ultra-compact footprints. Results indicate that our devices can provide excess loss (EL) of each output port of less than 3.3dB, 3.3dB and 3.6dB over 100 nm bandwidth at the centered wavelength of 1550 nm, respectively. Taking the footprints into consideration, we also design other two devices, which have the same functionalities as the latter two of the three devices mentioned above. Their ELs, less than 3. 6dB and 3.9dB, are slightly larger, but they have a big advantage in footprint. Especially, the idea of assembling simple devices into complex multifunctional devices is proposed. By this idea, the three 1 x 2 power splitters with different output directions can be freely assembled with each other according to actual application demand through certain rules and quantities, which can achieve arbitrary-direction, multichannel and ultra-compact power splitters. The EL of each port of the sample 1 x 4 splitter is less than 6.6dB and the ELs of the sample 1 x 3 splitter are less than 6.4dB, 6.4dB and 3.3dB, respectively.