Nano-Optical Switching of Photochromic Material through Ultraviolet and Visible Plasmon Nanofocusing

Optical control of photochromic properties is essential for optoelectronic devices. The manipulation of such properties has been limited to the microscale because of the wave nature of light; however, scaling down the volume is highly demanded for the future nanosized devices. Herein, we demonstrate optical switching at the nanoscale in an organic photochromic material. Photochromic materials such as diarylethene derivatives exhibit two different states with distinct optical and electronic properties under ultraviolet (UV) and visible light irradiation. We employed plasmon nanofocusing for optical switching of photochromic materials, which allowed the creation of a nanolight source at the apex of a tapered aluminum structure over a broad frequency range. We achieved in situ wavelength control between visible and UV light at the nanoscale for photochromic reactions. Using this technique, we demonstrated nanoscale optical switching between the two states of diarylethene. The switching performance was confirmed for at least nine cycles without degradation. This demonstration would constitute a significant step toward next-generation optoelectronic devices and benefit diverse scientific fields owing to the broad wavelength tunability of plasmon nanofocusing.