Heterogeneously Integrated Membrane Lasers and EAMs on Si Platform for Energy-Efficient Optical Link

This paper discusses the development of a photonic integration platform that leverages micro-transfer printing (MTP) and wafer-scale fabrication to integrate InP-based membrane lasers and electro-absorption modulators (EAMs) on silicon wafers. The platform aims to enable high-speed optical data transmission and energy-efficient optical links for next-generation communication systems, particularly in data centers and AI infrastructure.

Key Points from the Article:

1. Challenges and Solutions in Optical Interconnects:

• With the increase in demand for high-performance computing and data transfer, traditional electrical interconnects face physical and thermal limitations. The paper suggests that silicon photonics is a promising solution for optical interconnects, enabling efficient, high-density, and scalable optical communication.

• The integration of III-V materials (like InP-based lasers and modulators) with silicon photonics is essential for developing active components like light sources and modulators, which silicon alone cannot provide efficiently.

2. Two Photonic Integration Techniques:

• Micro-Transfer Printing (MTP): MTP is used for placing independently optimized III-V devices onto silicon photonic circuits. This method enables the use of known good dies and allows for device-specific optimization. The paper demonstrates the integration of a membrane DFB laser and EAM on Si waveguides using MTP, achieving 128-Gbit/s NRZ data transmission.

• Wafer-Scale Fabrication: This method enables the integration of membrane lasers, EAMs, and photodetectors (PDs) onto a single silicon wafer using lithographic processes. The integration allows for the creation of an optical link with low-loss SiOx waveguides, achieving an energy cost as low as 0.14 pJ/bit at 50-Gbit/s NRZ signaling. This method is more scalable and suitable for mass production.

3. MTP-Based High-Speed Optical Transmitter:

• The membrane DFB laser and EAM are integrated on silicon using MTP, with the laser operating at a wavelength of approximately 1295 nm. The devices show excellent performance, including a 3-dB bandwidth exceeding 50 GHz for the EAM and 128 Gbit/s NRZ data transmission.

• The integration process also includes the use of a polymer-based spot-size converter (SSC), which improves fiber coupling with low insertion loss. The MTP-based design is flexible and allows the independent optimization of each photonic component.

4. Wafer-Scale Integration of Optical Links:

• In contrast to MTP, wafer-scale integration offers the advantage of lithographically defined alignment of photonic components, making it ideal for high-volume production. The wafer-scale optical link integrates membrane laser, EAM, and photodetector onto a single silicon wafer.

• The membrane laser operates at low threshold currents (~1.7 mA), and the EAM achieves over 67 GHz of bandwidth. The entire optical link shows promising performance for high-speed communication, with the system demonstrating energy-efficient operation at 50 Gbit/s and 64 Gbit/s NRZ signaling.

5. Energy-Efficient Optical Link:

• The optical link demonstrates clear eye openings at 50 Gbit/s and 64 Gbit/s, with energy consumption of 0.14 pJ/bit at 50 Gbit/s and 0.26 pJ/bit at 64 Gbit/s, which are significant improvements over traditional electronic interconnects. These results highlight the potential of wafer-scale integration for energy-efficient, high-speed optical interconnects.

Conclusion:

The paper showcases the heterogeneous integration of III-V photonic devices (such as membrane DFB lasers and EAMs) on silicon photonics using MTP and wafer-scale fabrication methods. The integration enables high-speed optical data transmission (up to 128 Gbit/s) and energy-efficient operation (with a cost as low as 0.14 pJ/bit). The results demonstrate the scalability and flexibility of the technology, positioning membrane-based photonic integration as a promising solution for sustainable, high-performance optical interconnects in AI and data center infrastructures.