title: Shape-Dependent Nonlinear Optical Properties of Anisotropic Gold Nanoparticles.
abstract: This Letter reports the shape-dependent third-order nonlinear optical properties of anisotropic gold nanoparticles. We characterized the nonlinear absorption coefficients of nanorods, nanostars, and nanoshells using femtosecond Z-scan measurements. By comparing nanoparticle solutions with a similar linear extinction at the laser excitation wavelength, we separated shape effects from that of the localized surface plasmon wavelength. We found that the nonlinear response depended on particle shape. Using pump-probe spectroscopy, we measured the ultrafast transient response of nanoparticles, which supported the strong saturable absorption observed in nanorods and weak nonlinear response in nanoshells. We found that the magnitude of saturable absorption as well as the ultrafast spectral responses of nanoparticles were affected by the linear absorption of the nanoparticles.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hua
authors.forename: Kavita
authors.initials: K
authors.lastname: Chandra
authors.forename: Duncan Hieu M
authors.initials: DH
authors.lastname: Dam
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Gary P
authors.initials: GP
authors.lastname: Wiederrecht
authors.forename: Teri W
authors.initials: TW
authors.lastname: Odom
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006046:Gold
keywords: Z-scan; anisotropic metal nanoparticles; gold nanostars; hot electrons; nonlinear; saturable absorption