Extended Data Fig. 5: Electrostatically gated metasurface.
a, Metasurface device, with false colouring indicating the 3-nm/50-nm Ti/Au (light yellow), nanoantenna array (darker yellow), graphene (dark grey), 30-nm Pt back-gate electrode with 30-nm silica spacer layer (light grey) and substrate (light blue). b, Measured (solid line) and simulated (solid fill) reflectance spectrum of the device, showing resonant absorption around 875 nm. c, Gate-dependent photocurrent as a function of position, with locations indicated in a. Beam spot about 25 µm. To isolate the electrode contributions, the left and right electrode measurements are performed on an array-free device, with little laser polarization dependence observed. A polarity reversal is observed between the left and right electrodes. By contrast, strong polarization dependence is observed on the array at the centre of the sample. Both metasurface and array-free devices have 250-µm square graphene between the electrodes (metasurface device is the same as in Fig. 4). Photocurrents are normalized to the peak positive or negative values.