Abstract

The capability of polarization branching control of silicon-on-insulator horizontal slot waveguide-based directional couplers (DCs) was investigated, and a highly efficient polarization beam splitter (PBS) and a polarization-independent DC (PIDC) were proposed by tailoring the ratio of the coupling lengths for quasi-TE and quasi-TM modes. Due to structural birefringence, the coupling effects of the quasi-TE and quasi-TM modes in the DC may vary with the waveguide geometry. Numerical simulations were conducted to obtain the optimal design parameters for high efficiency and compact device size by varying the aspect ratios and waveguide spacing. The coupling lengths of the designed PBS and PIDC are 65.87 μm and 6.93 μm, respectively. They deliver good performance with extinction ratios of $\sim 20\mathrm{dB}$ for PBS and 15 dB for PIDC. The PBS and PIDC are also broadband with a 1 dB bandwidth larger than 30 nm and 100 nm, respectively. The fabrication-error tolerance of the practical device is also discussed.

© 2015 Optical Society of America

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