Ultrafast Third-Order Optical Nonlinearity in Au Triangular Nanoprism with Strong Dipole and Quadrupole Plasmon Resonance

Abstract

Au triangular nanoprisms have been prepared by the wet chemical method. By using absorption measurements and finite difference time domain (FDTD) calculations, the dipole and quadrupole plasmon resonances of Au triangular nanoprisms are investigated experimentally and theoretically. Calculations show that large electric fields are confined at the tips of the Au prisms, leading to large third-order optical nonlinearities. The Z-scan measurements show a third-order optical susceptibility of about 1.25 × 10–11 esu at 1240 nm, which is 19 times larger than that at 800 nm. The ultrafast light response time is about 482 fs measured by optical Kerr effect technique at 800 nm. The distinct third-order optical nonlinearities and the ultrafast response time enable the Au triangular prisms to be a good candidate for future all-optical switches and ultrafast optical information manipulators.