Optimizing polarization-diversity couplers for Si-photonics: reaching the −1dB coupling efficiency threshold

摘要: Polarization-diversity couplers are low-cost industrially-scalable passive devices that can couple light of unknown polarization from a telecom fiber-mode to pair TE-polarized wave-guided modes in the Silicon-on-Insulator platform. These offer significantly more relaxed alignment tolerances than edge-coupling schemes, which is advantageous for commercial fiber-packaging Si-photonic circuits. However, until now, polarization-diversity have not offered sufficient coupling efficiency motivate serious consideration. Using 3D finite difference time domain calculations device optimization, we identify with 1550nm efficiencies −0.95dB and −1.9dB, designs without bottom-reflector elements, respectively. significant improvement over state-of-the-art performance, effectively bridge “performance gap” between 1D-grating couplers. Our best coupler design goes beyond −1dB limit typically accepted as minimum needed industrial adoption telecoms market.