Near-Infrared Plasmonic Nanogap Organic Photodetectors for On-Chip Photonic Integration.

Near-infrared (NIR) photonic integrated circuits (PICs) are emerging as key platforms for on-chip optical communication and sensing, driven by their compatibility with silicon photonics and low-loss operation in telecom wavelength bands. However, conventional photodetectors based on Si, Ge, and III-V semiconductors require high-temperature processing and are difficult to integrate with polymeric or low-index photonic systems. Organic photodetectors (OPDs) offer a promising alternative, enabling efficient NIR light-matter interaction and photodetection while remaining compatible with low-temperature, solution-processed fabrication. Here, we demonstrate a plasmonic nanogap OPD architecture that enables efficient photodetection within an extremely confined nanoscale channel and direct integration with few-micron-width waveguides. Au/Al nanogap electrodes generate strongly localized plasmonic fields and facilitate efficient carrier extraction. With a photomultiplication-type bulk heterojunction, the device achieves high responsivity and quantum efficiency, along with ultralow dark current and a fast temporal response. The waveguide-integrated device detects guided optical signals at multimode interference outputs with consistent modulation response.