Ultra-compact low-loss 1 x 4 optical power splitter with splitting ratio of 1:2:4:8 based on two-stage cascaded MMI couplers

An ultra-compact low-loss 1 x 4 optical power splitter with a splitting ratio of 1:2:4:8 is proposed and demonstrated on a 220-nm-thick silicon-on-insulator (SOI) platform at the C band. The splitter is based on two stages of a cascaded 1 x 3 multimode interference (MMI) coupler and a 4 x 4 MMI coupler. The footprint of the device is 124.0 mu m x 6.4 mu m, which is more compact than the traditional scheme of four-stage cascaded 1 x 2 MMI couplers. Phase shifters based on taper waveguides are incorporated in the device as the connection of two MMI couplers. The fabricated device exhibits a 3 dB power difference with a deviation of less than 0.88 dB from 1530 nm to 1570 nm. The average power difference is 3.14 dB at the center of the C band with an insertion loss of 1.84 dB. (C) 2019 Optical Society of America