The rapid growth of large language models is placing increasing demands on data centers, where large volumes of data must be transferred efficiently between servers. Optical interconnects are essential for enabling this communication, but as data rates continue to rise, these systems must deliver higher bandwidth while maintaining low latency and energy efficiency. However, integrating electronic and photonic components remains challenging, as conventional approaches often introduce signal loss, limit interconnect density, and restrict scalability.
As reported in Advanced Photonics Nexus , Dr. Wei Chu and colleagues developed a reconfigurable germanium–silicon photodetector using a low-loss integration strategy based on fan-out wafer-level packaging (FOWLP). This approach enables seamless integration of electronic integrated circuits and photonic integrated circuits on a single platform without the need for traditional wire bonding, reducing parasitic loss and improving signal integrity.
The system uses a dense network of fine metal interconnects, known as a redistribution layer (RDL), to connect components with high precision. This structure supports high interconnect density—exceeding 10² connections per square millimeter—while maintaining a low insertion loss of less than 0.3 dB/mm at 100 GHz. In addition, the use of benzocyclobutene as a low-dielectric insulating material reduces transmission loss and improves thermal stability for reliable high-frequency operation.
Unlike conventional integration methods, which are often constrained by fixed chip layouts and inefficient interconnections, the proposed FOWLP-based approach enables greater flexibility in system design. It allows components from different sources to be integrated more easily while maintaining high performance, offering a scalable pathway toward next-generation co-packaged optical systems.
The photodetector demonstrates strong high-speed performance, with a bandwidth exceeding 110 GHz and efficient optical-to-electrical conversion. It also exhibits low-noise characteristics, including a dark current of approximately 7 nA and a responsivity of about 1 A/W at telecommunication wavelengths. These features contribute to stable and high-quality signal detection in high-speed communication systems.
To evaluate transmission performance, the researchers tested the device using multiple modulation formats, including NRZ, PAM4, PAM6, and PAM8. At a signaling rate of 112 Gbaud, the system supports data rates ranging from 112 Gbps to 336 Gbps per wavelength. Even at these high speeds, the device maintains strong signal integrity with minimal distortion, as confirmed by clear and open eye diagrams under different modulation conditions.
"These results show that low-loss RDL integration can preserve signal integrity even at ultrahigh-data rates. This is critical for enabling scalable optical interconnects in next-generation computing systems," says corresponding author Liang Zhou.
Overall, this work demonstrates how advanced packaging technologies can significantly improve the integration of optical and electronic components in large-scale computing environments. By enabling high-bandwidth, low-loss data transfer, the approach addresses key bottlenecks in AI infrastructure while improving energy efficiency and system scalability.
Looking ahead, continued optimization of the integration platform could further enhance performance and enable tighter coupling between electronic and photonic systems. Such advances may play an important role not only in AI data centers but also in future communication networks and high-performance computing platforms.
"This approach provides a practical pathway toward compact, energy-efficient, and scalable optoelectronic systems for future data-driven technologies," adds Zhou.
For details, see the original Gold Open Access article by A. Wang, Y. Huang, et al., " 336 Gbps silicon photodetector with a low-loss fan-out wafer-level heterogeneous redistribution layer ," Adv. Photon. Nexus 5(3), 036017 (2026), doi 10.1117/1.APN.5.3.036017
