Controlled surface-plasmon coupling in SiO2-coated gold nanochains for tunable nonlinear optical properties

Abstract

Linear chains of $\mathrm{Si}{\mathrm{O}}_2$ -coated Au nanoparticles, exhibiting large third-order nonlinearity at multiple wavelengths ranging from visible to near infrared, were successfully synthesized and self-assembled on glass substrates using a reduction of $\mathrm{H}\mathrm{Au}{\mathrm{Cl}}_4$ and chemical surfactant modification. The optical absorption spectra peaking at 530, 620, 715, 830, and $1100\mathrm{nm}$ wavelengths were measured to the transverse and longitudinal surface plasmon resonance modes of 2, 3, 4, and 5 Au particles, respectively. Greatly enhanced third-order nonlinear optical responses have been observed at multiple wavelengths.