Efficient WDM Laser Sources Towards Terabyte/s Silicon Photonic Interconnects

Abstract

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%.

Modeling and Evaluation of Chip-to-Chip Scale Silicon Photonic Networks

“…Optical fibers can be bidirectionally coupled to waveguides through vertical grating couplers [18] or taper couplers [19] to allow the networks to span multiple chips. These links are powered by multiwavelength laser sources [20]. The collection of these silicon photonic devices creates a platform for a diverse set of optical network implementations.…”

“…Because lasers cannot be turned on and off according the link activity, due to slow (millisecond) stabilization times, underutilized links are the major inhibitor to realizing very good power efficiency. Currently, the best laser source reported in literature in the CMOS-compatible silicon photonic platform operates with 4.5% power efficiency [20].…”

Wavelength-controlled external-cavity laser with a silicon photonic crystal resonant reflector

“…A particularly appealing feature of these is their support of Wavelength Division Multiplexing (WDM), which is a solution to the ever growing demands of bandwidth and integration in optical interconnections [1][2][3][4]. In order to exploit the advantages of WDM in Si photonics, it is crucial to obtain cheap, efficient, and Si-compatible tunable lasers with precise wavelength control [5].…”

“…An alternative solution is the formation of External-Cavity (EC) lasers by the use of external reflectors based on Si and Reflective Semiconductor Optical Amplifiers (RSOAs). The latter approach has the advantage of allowing independent design, fabrication and optimization cycles for the active and passive components, making a more effective use of the III-V materials [5,7].…”

“…This represents a step forward in the pursuit of laser architectures with small footprint, high Side-Mode Suppression Ratios, and high precision peak wavelength control, all of which are requirements for efficient WDM applications [5].…”