Role of photoinduced destruction of gold nanorods in the formation of nonlinear optical response

Abstract

In this work, we investigated the nonlinear optical response of ensembles of gold nanorods (Au NR) with an average size of 6 × 18 nm dissolved in water, passivated with cetyltrimethylammonium bromide (CTAB). Negative nonlinear refraction with an index γ = –3.5·10−15 cm2·W−1 and nonlinear absorption were found using Z-scan technique in a field of the second harmonic of 10 ns YAG:Nd3+ laser pulses with a wavelength of 532 nm. The Z-scan profile demonstrates the samples bleaching as well as an increase in absorption near the lens focal plane in the case the pulse energy increases to 0.16 mJ. It was shown that the sample bleaching is caused by a decrease of optical density at a wavelength of 532 nm as a result of the photoinduced transformation of nanoparticles from cylindrical to a spherical shape passing through the melting stage.