Comparing Laser Hybrid-Integration and Fiber Coupling With Standard Grating Couplers on Si-PICs

We compare the simulated optical insertion-losses and fabrication-tolerances of a micro-optical bench (MOB) for laser hybrid-integration on the 220-nm silicon-on-insulator (SOI) photonic-platform to standard fiber-to-grating coupling. Our millimeter-scale two-dimensional finite-difference time-domain (2D-FDTD) simulation captures: 1) aberration; 2) reflection; 3) diffraction; and 4) wave-guiding effects in a single-shot and completely self-consistent way, indicating that light from a laser-diode can be coupled to the SOI photonic integrated circuit (PIC) with a 2.8-dB insertion-loss at 1550 nm. This insertion loss is just 1 dB higher than for a standard fiber-to-PIC grating-coupler, and is due to a combination of interface-reflections and aberration-effects from the micro-optical elements in the MOB. We use further 2D-FDTD simulations to investigate the alignment and manufacturing tolerances of the MOB and show that these are compatible with practical photonic-packaging processes for mass-manufacture.