Furthermore, while photon information storage has been described in the literature as extremely difficult on all-optical processing 13, nanoscale photochromism coupled with optical near-fields naturally enables memorization based on the intrinsic attributes of photochromic materials. Therefore, nanometre-scale optical functionalities are likely to be achievable using diarylethene crystals. The local photoisomerization triggered by near-field optical excitation of diarylethene crystals progresses in a complex manner along with branching and multivaluedness by spontaneous symmetry-breaking associated with anisotropic distortion on the nanometre scale, depending on the dynamic changes of the material structures, that is, environmental singularities. By performing theoretical analysis, we showed that the decision-making architecture must include branching and multivaluedness 12. On the macroscopic scale, we previously succeeded in demonstrating decision-making functions using single photons 2. Ultimately, our objective is to realize novel optical functions on the nanometre scale using local distortions and photoisomerization in diarylethene crystals induced by near-field optical excitation. In this article, we report on the optical near-field-induced, nanometre-scale photoisomerization observed on the surface of a diarylethene crystal as the local surface shape changed.īefore proceeding, we remark upon the concept behind our research. The distortion suppresses the spreading of the photoisomerization to the surroundings, thereby maintaining the locality of the photoisomerization.
Moreover, upon near-field optical excitation of diarylethene crystals, the large momentum of the optical near-field 7, 8, 9 causes local photoisomerization 10, 11, specifically, collective photoisomerization of the neighbouring molecules, leading to nanometre-scale mechanical distortion. Among these materials, diarylethene is a promising vehicle because it is thermally stable and exhibits photochromic reactions in a crystalline state 6. The reversible photoisomerization of photochromic materials is useful in functional optical systems. The unique physical attributes of light–matter interactions have recently been intensively studied with the objective of developing novel intelligent functionalities such as decision making 1, 2, solution searching 3, and cognition 4, 5, among others.