All-Silicon Dual-Wavelength Hot-Electron Photodetector with Quasi-Omnidirectional Schottky Interface for Ultralow-Noise Equivalent Power Encrypted Demultiplexing Telecommunication

Sub-bandgap photodetection on all-silicon platforms through harvesting hot electrons from the nonradiative decay of surface plasmons presents significant potential for CMOS-compatible optoelectronics, enabling self-powered room-temperature operation. However, the device performance is still limited by the high noise equivalent power (NEP), and conventional single narrowband photodetection responses cannot meet the requirements for encrypted wavelength-division demultiplexing in telecommunication. We address these challenges by developing a tunable dual-wavelength hot-electron photodetector with a record-low NEP performance across the telecommunication bands. Our design integrates plasmonic nanoholes with silicon nanowires, establishing a synergistic dual-resonance mechanism─enhancing plasmonic field intensity by 2 orders of magnitude while forming quasi-omnidirectional Schottky interfaces for efficient hot carrier confinement and collection. The device exhibits a dual narrowband photoresponse with spectral tunability across telecommunication wavelengths (O to L bands), achieving unprecedentedly low NEP values ranging from 8.8 × 10–13 W·Hz–0.5 to 2.3 × 10–12 W·Hz–0.5. As a proof of concept, we demonstrate encrypted demultiplexing in telecommunications using a dual-wavelength photodetector. This work paves the way for low-cost, all-silicon sub-bandgap photodetection and provides a scalable platform for integrated silicon photonics in secure communication systems and on-chip spectral sensing applications.