  We demonstrate history-dependent or dynamic nano-photoisomerization by
sequential formation of multiple memory pathways in photochromic crystals via
optical near-field interactions. We observed the incident photons passing
through the photoisomerization memory pathways by a double-probe optical
near-field microscope, with one probe located on the front surface for local
excitation and the other on the rear surface for near-field observation. By
carrying out localized near-field excitation twice but at spatially different
positions, we observed negatively correlated near-field output patterns between
the first memory pathway and the second memory pathway. That is, the added
memory pathway was formed exclusively to the previously formed memory pathway.
We also confirmed that the first memory pathway was preserved after the second
memory pathway was formed. This result indicates that photoisomerization by an
optical near-field in diarylethene crystals has a history dependence, leading
to brain-like dynamic information memorization using light-matter interactions
on the nanometer-scale.
