Waveguide-Integrated Johnson Noise Readout Bilayer Graphene Bolometers

Graphene bolometers based on Johnson noise readouts operating at zero bias can eliminate both the measurement instability and insufficient linearity in the conventional photoresistance-readout devices. Featuring simple structure, large-scale integrability, and broadband operation, they are promising for on-chip high-sensitivity detection. Nevertheless, related studies remain limited, and systematic waveguide-integrated demonstrations are still absent. Here, the silicon waveguide-integrated Johnson noise readout graphene bolometers are demonstrated to achieve efficient on-chip light-graphene interactions. A system-level model has been established, revealing the effects of graphene electron heat capacity, circuit integration time, operating temperature, and other factors on detection performance. At room temperature, the system accurately measures optical power from 269 pW to 6.7 mW, achieving an NEP of 185 pW·Hz –0.5 at 1.55 μm. The results demonstrate that our device outperforms conventional surface-illuminated counterparts. The highly repeatable experimental data exhibit better stability and robustness than conventional photoresistance-readout graphene bolometers operating under bias voltage. In the future, this work can be extended to longer wavelengths and facilitate the optoelectronic integration of devices and readout circuits, providing an important solution for broadband silicon integrated high-sensitivity photodetection for applications of on-chip optical power monitoring, sensing, spectroscopy, etc.