Research progress of waveguide integrated carbon based infrared detectors

<sec>Carbon-based materials, such as graphene and carbon nanotubes (CNTs), have garnered significant attention for next-generation infrared photodetection due to their unique and excellent physical properties, including ultra-high carrier mobility and exceptionally broad spectral absorption. These characteristics present vast application prospects in fields such as optical communications, military sensing, biomedical imaging, and energy. However, a critical bottleneck for their practical application is the inherently weak light-matter interaction stemming from their low-dimensional nature. For example, a single layer of graphene absorbs only 2.3% of incident light, which severely limits the sensitivity and overall performance of photodetectors.</sec><sec>To overcome this fundamental limitation, integrating carbon-based materials with photonic waveguides has emerged as a highly effective and promising strategy. This approach confines light within the waveguide and utilizes the evanescent field to couple with the carbon material over a long interaction length, greatly enhancing the total light absorption. Furthermore, its intrinsic compatibility with CMOS fabrication processes paves the way for low-cost, high-density, and large-scale manufacturing, meeting the stringent demands of future optoelectronic systems.</sec><sec>This paper comprehensively reviews the latest developments in waveguide-integrated carbon-based infrared photodetectors, systematically summarizing and analyzing the progress made in three major integration aspects: silicon-on-insulator (SOI), silicon nitride (SiN<sub><i>x</i></sub>), and advanced heterostructures such as plasmonic and slot waveguides). Various performance enhancement strategies are detailed by exploring different photodetection mechanisms, including the photovoltaic effect (PVE), photothermoelectric effect (PTE), photobolometric effect (PBE), and internal photoemission effect (IPE). Key breakthroughs are highlighted, such as achieving ultra-high bandwidths exceeding 150 GHz on SOI, realizing a superior balance of high responsivity (~2.36 A/W) and high speed (~33 GHz) on SiN<sub><i>x</i></sub>, and enhancing responsivity to over 600 mA/W while extending the detection range to the mid-infrared (5.2 μm) using advanced heterostructure waveguides.</sec><sec>Finally, the current development bottlenecks are discussed, including challenges in material transfer, interface quality control, and thermal management. Future research directions are also suggested, such as the development of novel carbon-based heterostructures, deeper integration with on-chip photonic systems, and the exploration of new waveguide materials for long-wave infrared applications. This work provides a clear roadmap for the continously developing high-performance, waveguide-integrated carbon-based infrared detectors.</sec>