High responsivity nano-air-channel photomixer for mmWave generation

Photomixer with high-speed and large-bandwidth is a key device for photoelectric conversion in photonic millimeter wave and terahertz information system. Herein, for the first time, nano-air-channel photodiode is demonstrated as a photomixer to generate coherent mmWave signal in experiment. Based on the external photoelectric effect, photoelectrons emitted from the InGaAs photocathode can reach the metal anode by scattering-free ballistic transport in the quasi-vacuum nano-air channel, resulting in a high-speed response. The large electric field nearby the nano-air channel led to carrier multiplication inside the InGaAs, which enables a high responsivity. This work provides a new type device which has great potential to break through the limits of the traditional semiconductor photomixers in bandwidth, efficiency and output power.