SiN_x Waveguide-Integrated Carbon Nanotube Photodetector with Bandwidth over 67 GHz Operating at 1.55 and 2 μm Band

As data transmission rates scale toward unprecedented capacities, both the conventional 1.55 μm telecommunication band and the emerging 2 μm band require photodetectors with large electrical bandwidth and high responsivity. Although mature Ge- and III-V-based photodetectors can operate fast at 1.55 μm band, there cannot work efficiently at 2 μm band because of band gap and material quality. Here we report a waveguide-integrated carbon nanotube (CNT) photodetector on a silicon nitride (SiN_x) platform that delivers high performance across both wavelength regimes. At 1.55 μm and a bias of -1 V, the device exhibits a 3 dB bandwidth exceeding 67 GHz. At 2 μm, it maintains a low dark current of 80 nA and a responsivity of 0.41 A/W, while delivering a similarly setup-limited 3 dB bandwidth beyond 67 GHz. This bandwidth represents a significant leap over previously reported photodetectors operating in this spectral regime. Our findings position CNT photodetectors as a promising platform for CMOS-compatible, high-speed optical interconnects across both the 1.55 and 2 μm bands. Furthermore, the demonstrated high-speed performance underscores their potential to underpin the next generation of large-scale photonic and optoelectronic integrated circuits (OEICs).