Broadband Arbitrary Ratio Power Splitters based on Directional Couplers with Subwavelength Structure

We propose and demonstrate a $1\times2$ power splitter enabling arbitrary power splitting ratios. The device is based on a directional coupler with subwavelength structure in the coupling region and a trapezoid-structure in one arm. The measurement shows that arbitrary power splitting ratios, equal to 50:50, 60:40, 70:30, 80:20 and 90:10, can be obtained over an >80 nm bandwidth with an excess loss about 0.65 dB at 1550 nm, while the footprint is only $11.5\,\,\mu \text{m}\,\,\times 1.315\,\,\mu \text{m}$ . The proposed arbitrary ratio power splitter shows promising application prospect in photonic integrated circuits.