Wavelength-dependent laser-induced dynamic nano-annealing of single plasmonic antennas

In this work, we studied the wavelength-dependent laser-induced dynamic annealing of single plasmonic nano-antennas using in situ white light spectroscopy. Unexpected back-and-forth motions of rapidly melted single nano-antennas were observed upon excitation with a 532 nm laser, while only gradual opening of nanogaps was found in the case of a 405 nm laser. Theoretical analyses indicate that the dramatic nano-annealing phenomenon was caused by a series of laser-induced multiphysical processes at the nanoscale. It not only leads to the local heating effect, but also induces complex behaviors such as self-accelerated melting, asymmetry-induced nano-photophoretic forces and optical forces. Our work demonstrates the complexity of light-matter interactions at the nanoscale, and provides new possibilities for shaping and manipulating plasmonic nanostructures.