Dive in to know how researchers developed a germanium-implanted photodiode that detects on-chip light signals with minimal loss, noise and power consumption.
As programmable photonics use light instead of electrons to transmit and process signals, they promise faster, more energy-efficient computing for applications like real-time AI and data-intensive tasks. However, these systems rely on precise on-chip light monitors to adjust and maintain performance. Existing photodetectors face a fundamental challenge: they must detect very weak signals while allowing most light to pass through without loss, all while keeping noise and power consumption low. Balancing these requirements has limited the effectiveness and scalability of programmable photonic circuits.
Researchers at the Hong Kong University of Science and Technology (HKUST) have addressed this challenge by developing a germanium-ion-implanted silicon waveguide photodiode. Integrated directly into optical waveguides, the device converts a small portion of light into an electrical signal without disturbing the main optical path. Germanium ions, compatible with silicon’s crystal lattice, enhance photon absorption across key telecom wavelengths (1,310 nm and 1,550 nm) without introducing free carriers that degrade performance.
Comparative tests show that the new photodiode achieves high responsivity, ultra-low optical loss, and minimal dark current, outperforming existing on-chip linear photodetector platforms. Its low-bias, low-noise characteristics make it suitable not only for programmable photonics but also for energy-efficient, ultra-sensitive biosensing and lab-on-chip systems.
Key features of the research include:
- Germanium-ion implantation for broad-wavelength absorption without free-carrier degradation
- High responsivity at telecom O- and C-band wavelengths
- Ultra-low dark current for minimal background noise
- Low optical loss for seamless waveguide integration
- Potential applications in biosensing and lab-on-chip technologies
Prof. Andrew Poon, Head of HKUST’s Department of Electronic and Computer Engineering, concludes, “This study demonstrates a practical, high-performance solution for on-chip light monitoring, bringing the transformative potential of programmable photonics closer to reality and opening new possibilities for biosensing and lab-on-chip systems.”
