Ultra-broadband high-performance polarizing beam splitter on silicon

A high-performance silicon-based polarizing beam splitter (PBS) is proposed and demonstrated experimentally by using an improved structure with cascaded bent directional couplers. The measured extinction ratio (ER) is >35dB and the excess losses (EL) is 2. The measured bandwidths for an ER of >20dB, >25dB and >30dB are ~135nm, ~95nm and ~70nm, respectively, while the measured EL is <1dB and <0.5dB in a bandwidth of ~140nm and ~85nm, respectively. The fabrication tolerance of the core-width variation is as large as ± 40nm, which makes the fabrication very easy.