Widely-tunable, narrow-linewidth III-V/silicon hybrid external-cavity laser for coherent communication

Area of Science:

• Photonics and Semiconductor Devices
• Integrated Optics
• Optical Communications

Background:

• Silicon photonics offers a scalable platform for integrated optical devices.
• External cavity lasers are crucial for tunable optical communication systems.
• Hybrid integration of III-V materials with silicon enhances laser performance.

Purpose of the Study:

• To demonstrate a hybrid III-V/silicon external cavity laser on a silicon-on-insulator (SOI) platform.
• To achieve a wide tuning range (C-band) and narrow linewidth for optical communications.
• To showcase a complete silicon photonics-based coherent optical link for high-speed data transmission.

Main Methods:

• Hybrid integration of a III-V semiconductor gain chip with a silicon photonic chip using edge-coupling and Si3N4 spot size converters.
• Passive alignment packaging suitable for high-volume manufacturing.
• Characterization of laser performance including tuning range, output power, efficiency, side-mode suppression ratio, and linewidth.
• Demonstration of a 34 Gbaud (272 Gb/s) dual-polarization 16-QAM transmission using the integrated laser and a silicon photonic coherent transceiver.

Main Results:

• Achieved a tuning range greater than 60 nm covering the C-band.
• Maximum output power of 11 mW and a wall-plug efficiency of 4.2%.
• Side-mode suppression ratio exceeding 55 dB and a narrowest linewidth of 37 kHz (narrowest for silicon-based external cavities).
• Successful demonstration of 272 Gb/s coherent optical transmission with no penalty compared to commercial lasers.
• First experimental demonstration of a complete silicon photonic coherent link and >250 Gb/s transmission using a silicon micro-ring-based tunable laser.

Conclusions:

• The hybrid III-V/silicon external cavity laser is a viable solution for high-performance, tunable light sources in optical communications.
• The demonstrated packaging method supports scalable, high-volume production.
• This work represents a significant advancement towards fully integrated silicon photonic systems for high-speed data transmission.