Near-field properties of a gold nanoparticle array on different substrates excited by afemtosecond laser

Abstract

In this paper we present experimental and theoretical results on the properties ofthe electromagnetic field in the near-field zone of gold nanoparticles excited byan 800 nm ultrashort laser pulse. The near-field properties are studied for thecase of a single isolated particle and 2D nanoparticle array case. Particles aredeposited on different substrates: metal (Au), semiconductor (Si) and dielectric(SiO2). The calculations based on the finite difference time domain (FDTD) simulation techniquepredict that the field in the vicinity of the particles is enhanced as the magnitude of thefield intensity depends on the substrate material and the interparticle distance for 2D array.For closely arrayed nanoparticles on the gold substrate, the maximal field intensity is morethan two times lower than that of a single particle. With the increase of the distancebetween 200 nm diameter gold particles, the value of the field intensity increases up to adistance of about 800 nm. The theoretical prediction of the field enhancement on thesubstrate is confirmed experimentally. The irradiation of the nanoparticles depositedon the three different substrates with a single laser pulse of a Ti:sapphire laserresults in a nanohole formation. Discussion on the observed properties is presented.