All-Optical-Input Transistors: Light-Controlled Enhancement of Plasmon-Induced Photocurrent

Although phototransistors for controlling photocurrent with electricity have been studied intensively for several decades, transistors with all-optical inputs that can control the photocurrent with light have not been investigated thus far. In this paper, a plasmonic porous Ag/TiO2 transistor is fabricated with all-optical inputs. One light input acts as the source to generate a plasmonic-hot-electron photocurrent, while the other gate light changes the current channel by adjusting the height of an Ag/TiO2 Schottky barrier. As a result, the plasmon-induced photocurrent generated by the source light can be enhanced by several to one hundred times by controlling the gate light. In addition to signal enhancement, the device can also be used for signal modulation and switching.