Yu He Yong Zhang 0035 Xiaodong Wang Boyu Liu Xinhong Jiang Ciyuan Qiu Yikai Su Richard A. Soref Silicon polarization splitter and rotator using a subwavelength grating based directional coupler. 1-3 2017 OFC https://ieeexplore.ieee.org/document/7936929 conf/ofc/2017 db/conf/ofc/ofc2017.html#HeZWLJQSS17