Nanocomposite systems based on bismuth nanoparticles (Bi NPs) have received a growing interest due to the demonstration of plasmon-like resonances that can be tuned in the visible-UV region, and that have found applications for integrated photonic devices, surface enhanced spectroscopy and plasmonic enhanced photocatalysis.[1,2] Furthermore, due to the low melting temperature of Bi, these systems are also candidates for its use as optical switches by profiting from the different optical properties of solid and liquid Bi [3]. Here we study the solid-liquid phase change of Bi NPs embedded in amorphous aluminium oxide film upon nanosecond laser excitation by using single pulse real time reflectivity measurements with nanosecond resolution. The changes of the reflectivity reveal that melting takes place within the nanosecond pulse duration whereas cooling and solidification of the NPs occurs over time scales that are much longer than for bulk Bi. The solid-liquid switching time is found to depend on the nanoparticle density, and it can be controlled smoothly from 10 ns to 700 ns by adjusting the laser pulse fluence. The optical switching process is found to be repeatable more then 10,000 times without observable degradation. [1] J. Toudert, et al. J. Phys. Chem. C 121, 3511 (2017). [2] J. Toudert and R. Serna, Opt. Mater. Express 7, 2299 (2017). [3] M. Jiménez De Castro, F. Cabello, J. Toudert, R. Serna, and E. Haro-Poniatowski, Appl. Phys. Lett. 105, (2014).

Spring Meeting of the European Materials Research Society (E-MRS): IUMRS - ICAM International Conference on Advanced Materials, Nice (Frane) May 27 - 31, 2019