The multimode power splitter is a fundamental component in mode-division multiplexed systems. In this paper, we design and characterize a broadband compact dual-mode multimode interferometer (MMI) optical power splitter based on subwavelength grating (SWG) structures. The optimized dual-mode MMI is three times more compact than its conventional mode insensitive MMIs and shows low loss and low crosstalk flat response over 100 nm bandwidth. Characterizations of the fabricated dual-mode splitter show that the total excess loss in the experiment is less than 0.1 dB and 0.65 dB for TE0 and TE1, respectively, and the modal crosstalk is less than -17 dB for both input modes.