Compact, Ultra-broadband and Fabrication Tolerant Adiabatic 3-dB Coupler Based on Silicon-on-insulator Rib Waveguides

We propose an adiabatic 3dB coupler based on rib waveguide, which has the characteristics of low loss, compactness, large bandwidth and excellent fabrication tolerance. The proposed devices exhibit a minor coupling length of 78 μm and a flat-broad operating bandwidth of 200 nm with a low loss of 0.16dB. The fabrication analysis confirmed that they are robust to fabrication errors.