Regular paper

Near-infrared light absorption and scattering based on a mono-layer of gold nanoparticles

¹ Optics and Photonics, School of Information and Communication Technology, KTH - Royal Institute of Technology, Isafjordsgatan 22, Kista 164 40, Sweden
² ACREO Swedish ICT AB, Isafjordsgatan 22, Kista 164 40, Sweden
³ State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, 310027 Hangzhou, China

^* miya@kth.se

Received: 8 March 2015
Revised: 8 June 2015

Abstract

We report fabrication and characterization of large-area ultrathin near-infrared light absorbers and scatterers based on a mono-layer of gold nanoparticles laying on top of a dielectric spacer and an aluminum reflector. The nanoparticles are formed through thermal annealing of an evaporated continuous gold film. Through optimization of initial gold-film thickness, spacer thickness, as well as annealing temperature we obtained samples that exhibit very low (~2%) broadband specular reflectance at near-infrared (NIR) wavelength range. By considering also diffuse reflection, we identify that the low specular reflectance can be due to either relatively high light absorption (~70%) or high light scattering (over 60%), with the latter achieved for samples having relatively sparse gold nanoparticles. Both strong absorption and scattering of NIR light are not inherent properties of the bulk materials used for fabricating the samples. Such composite optical surfaces can potentially be integrated to solar-energy harvesting and LED devices.