Ultra-Broadband Dual-Polarization Power Splitter Based on Silicon Subwavelength Gratings

We demonstrated an ultra-broadband dual-polarization power splitter based on silicon subwavelength gratings (SWGs). Multimode interference (MMI) couplers based on SWG are utilized for power splitting. SWGs with different orientations are combined to form a taperized hetero-anisotropic slab, which contains single mode for TE light but multimode for TM light. Such configuration is utilized to make it possible to design the coupling length of TE light and TM light separately. The geometry parameters such as numbers of periods and duty cycles for the SWGs are engineered to make the two-fold images of different wavelengths and two polarizations located at the same position, which will result in low loss and large bandwidth. Both the simulation and measurement results show that the proposed device can work over a large bandwidth of 420 nm (1.26 ~ 1.68 μm) with loss lower than 1 dB. The footprint of the proposed device is quite small (18.4 μm × 2.8 μm).