Ultrafine Modulation of Plasmon Resonance in Single Gold Nanorods via Photothermal Effects

The real-time active control of plasmonic properties is desirable for advanced applications in photochemical reactions and nano-optical devices. In this study, we investigated the morphology and optical properties of a single gold nanorod under laser irradiation. We observed a blue shift in the plasmon resonance after laser irradiation. Furthermore, electron micrograph analysis revealed that this shift occurred due to the transformation of the nanorod shape. We also examined the time-evolution of the resonance wavelength under laser irradiation, and we found that the resonance wavelength could be reversibly modulated through controlled laser irradiation. Electromagnetic field simulations showed that the reversible modulation behavior was achieved by the thermal expansion and shrinking of the nanorod. Moreover, we demonstrated the ultrafine modulation of the resonance as well as the physical shape of the nanorod with the subnanometer accuracy. The method developed in this study paves the way for the precise and ultrafine modulation of plasmon resonance and is indispensable for advanced control of light-matter interactions at the nanoscale.