Optical Imaging of Quantum Hall Current in GaAs/AlGaAs Two‐dimensional Electron System

We have measured the current distribution in GaAs/AlGaAs two‐dimensional electron system at quantum Hall effect regime, where the critical current shows sub‐linear dependence on the channel width. An optical‐fiber‐based potential imaging system by Pockels effect is improved by using a twin‐optical bridge detector which reduces retardation noise in the optical fiber. We have also mapped the resistance change by the local photo‐excitation in the QHE regime. Both the observed images show the evidence of current concentration at center region of the channel, and the extent of current concentration increases with increasing the current.