Efficient WDM Laser Sources Towards Terabyte/s Silicon Photonic Interconnects

Efficient multi-wavelength sources are essential to realize sub-pJ/bit modulated silicon photonic links for multi-TB/s interconnect applications. From a complete link perspective, we discuss the efficiency requirement for silicon WDM on-chip sources. A waveguide-coupled wall-plug efficiency (WPE) better than 10% is important to complement ultra-low power silicon photonic components for practical implementations. We propose a non-invasive hybrid, flip-chip integration approach using surface-normal coupling of an un-cooled III/V gain medium with a tunable wavelength selective silicon reflector. We show that a tunable, external-cavity WDM laser using such a hybrid integration approach can achieve high waveguide-coupled WPE when optimized. A proof-of-concept demonstration achieved a C-band tunable laser with an output power of more than 6 mW in the silicon waveguide, a tuning range of 15 nm, and a WPE of over 4.5%.