Demonstrating nanophotonic switching using near-field pump-probe photoluminescence spectroscopy of CuCl quantum cubes.

We demonstrated a novel optical switching operation using three CuCl quantum cubes with a size ratio of. Their quantized excitonic energy levels resonate with one another, and the switching mechanism was based on the resonant near-field energy transfer between the quantum cubes. Using near-field pump-probe photoluminescence spectroscopy, we succeeded in controlling the near-field energy transfer and obtained a controlled (i.e. switched) signal in a differential photoluminescence spectrum with and without a pump beam. The internal quantum efficiency of the switching operation was close to 1. These results suggest the possibility of making a nanophotonic switching device smaller than 30 nm.