Nonlinear Optical Properties of Silver Nanocrystals with Different Shapes

Silver nanocrystals with prism and disk shapes have been synthesized by the light-driven growth method in an aqueous solution. Nonlinear optical properties of these two samples were investigated by home-built femtosecond Z-scan system with 800 nm incident wavelength. The Ag nanoprisms with 75 nm size show 700 nm SPR peak and exhibit both negative and positive nonlinear absorption. The nonlinear absorption process is considered to be generated by ground-state plasmon bleaching, free-carrier absorption, and inter-band transitions. The Ag nanodisks with 35 nm size show 495 nm SPR peak. However, Ag nanodisks display only positive nonlinear absorption process. The different nonlinear absorption process is attributed to the morphology influence by the Ag nanocrystals.