Polarization-Insensitive Ultrasmall Microring Resonator Design Based on Optimized Si Sandwich Nanowires

Bent Si sandwich nanowires are used and optimized to obtain an ultrasmall polarization-insensitive microring resonator (MRR). The used Si sandwich nanowire has a low refractive index layer between two Si layers with high refractive indexes. By optimizing the refractive index and thickness of the sandwiched layer, the bent Si sandwich nanowire becomes nonbirefringent theoretically. The designed nonbirefringent nanowire has a relatively good fabrication tolerance. By using such a nonbirefringent bent Si sandwich nanowire, an ultrasmall polarization-insensitive MRR is designed.