High-Speed EML and Assembly Techniques for GPU Cluster System

In this paper, we present the development of high-speed Electro-Absorption Modulated Laser Diodes (EMLs) and advanced assembly techniques tailored for GPU cluster systems. The increasing computational demands driven by generative AI and large language models necessitate significant advancements in data transfer speeds within data centers. We introduce a high-mesa structure for the Electro-Absorption Modulator (EAM) within the EML, achieving superior modulation efficiency and bandwidth. The EML is designed for 400 Gbps/lane modulation, addressing the need for higher data rates such as 3.2 Tbps pluggable transceivers. To achieve 400 Gbps/lane, we fabricated and demonstrated EMLs with narrow mesa widths of 1.1 μm and 0.8 μm in the high mesa structure. Achieving 400 Gbps requires a modulation bandwidth exceeding 100 GHz, which poses a significant challenge to the assembly. We propose an advanced EML assembly that includes a Glass-AlN hybrid submount to overcome these limitations. This hybrid submount significantly reduces the parasitic inductance of the wire bonding and enables the adoption of low dielectric material for RF trace, achieving higher modulation bandwidth. Our prototype demonstrates a 3 dB bandwidth exceeding 100 GHz, both numerically and experimentally. Additionally, targeting Near Package Optics (NPO) and Co-Packaged Optics (CPO) with high edge density, we investigate packaging technology that eliminates the need for wire bonding. Our prototype demonstrated a 3 dB bandwidth of 85 GHz and a clear eye opening for 113.4 GBaud PAM4 signals. These innovations pave the way for future high-density photonics-electronics convergence technologies, essential for next-generation optical interconnects in high-performance computing environments.