Processes underlying the laser photochromic effect in colloidal plasmonic nanoparticle aggregates**Project funded by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science (Grant 18-42-243023), the RF Ministry of Science and Higher Education, and the State Contract with Siberian Federal University for Scientific Research. A.E. thanks the grant of the President of

Abstract

We have studied the dynamic and static processes occurring in disordered multiparticle colloidal Ag aggregates with natural structure and affecting their plasmonic absorption spectra under pico- and nanosecond pulsed laser radiations, as well as the physical origin responsible for these processes. We have shown that depending on the duration of the laser pulse, the mechanisms of laser modification of such aggregates can be associated both with changes in the resonant properties of the particles due to their heating and melting (picosecond irradiation mode) and with the particle shifts in the resonant domains of the aggregates (nanosecond pulses) which depend on the wavelength, intensity, and polarization of the radiation. These mechanisms result in formation of a narrow dip in the plasmonic absorption spectrum of the aggregates near the laser radiation wavelength and affect the shape and position of the dip. The effect of polydispersity of nanoparticle aggregates on laser photochromic reaction has been studied.