Frequency conversion is the common approach for signal processing required in various communication applications. However, nowadays frequency conversion with traditional nonlinear electronic components has found its bottleneck due to the limited operation bandwidth. At the same time, fiber-optic communications have played a significant role in communication services due to its excellent optical transmission properties. And the transmitted optical signals had to be converted to electrical signals with photodetectors before frequency conversion was performed through conventional electronic devices, which make this conversion system very complex and costly. Hence to invent a compact device that can achieve the photodetection and frequency conversion functions simultaneously is critical and significative. Here, a graphene photodetector (GPD) was first utilized to perform frequency conversion from optical signals directly. Using an 80 MHz intensity-modulated optical signal and another 3 GHz intensity-modulated optical signal, we show frequency up-conversion to 3±0.08 GHz. And using an 80 MHz intensity-modulated optical signal and another 100 MHz intensity-modulated optical signal, we show frequency down-conversion to 20 MHz. Considering the broadband optical absorption [1], strong saturable absorption [2], high carrier mobility [3], and short photogenerated carrier lifetime [4] of graphene material, GPDs have the potential to achieve frequency conversion of millimeter-wave band, which will open promising perspectives in the domain of microwave photons for the next-gen communication systems.

Frequency conversion is the common approach for signal processing required in various communication applications. However, nowadays frequency conversion with traditional nonlinear electronic components has found its bottleneck due to the limited operation bandwidth. At the same time, fiber-optic communications have played a significant role in communication services due to its excellent optical transmission properties. And the transmitted optical signals had to be converted to electrical signals with photodetectors before frequency conversion was performed through conventional electronic devices, which make this conversion system very complex and costly. Hence to invent a compact device that can achieve the photodetection and frequency conversion functions simultaneously is critical and significative. Here, a graphene photodetector (GPD) was first utilized to perform frequency conversion from optical signals directly. Using an 80 MHz intensity-modulated optical signal and another 3 GHz intensity-modulated optical signal, we show frequency up-conversion to 3±0.08 GHz. And using an 80 MHz intensity-modulated optical signal and another 100 MHz intensity-modulated optical signal, we show frequency down-conversion to 20 MHz. Considering the broadband optical absorption [1], strong saturable absorption [2], high carrier mobility [3], and short photogenerated carrier lifetime [4] of graphene material, GPDs have the potential to achieve frequency conversion of millimeter-wave band, which will open promising perspectives in the domain of microwave photons for the next-gen communication systems.