Figure 4. Detecting local electric field fluctuations with spatial and temporal resolution.

(a) Geometry of the experimental set-up in which a waveform is applied to a 2 μm platinum/iridium microelectrode placed in solution 5 μm above the graphene surface of the detector. Applying a waveform to the microelectrode generates a spatially distributed electric field pattern and permits observation of the local electric field modulation in space and time. (b) Temporal dynamics of the experimental (solid) and simulated (dashed) optical CAGE detection of the local electric field at different distances from the local potential source. The local field is generated by a 10 mV 200 ms pulse (red) applied to the microelectrode. The spatial location of A1 (yellow), A2 (green) and A3 (blue) is articulated by white dashed lines in c. (c) CAGE image with spatio-temporal resolution of the first 70 ms of local electric field dynamics described in b projected onto a one-dimensional 193 Hz InGaAs camera. The spatially resolved recording obtains ∼100 μV sensitivity with 5 ms temporal resolution.