Retrieval of the effective complex refractive index of Bruggeman nanoliquids from surface plasmon resonance reflectance using the maximum entropy method

Abstract

We show that surface plasmon resonance reflectance measurement can be used to extract the effective complex refractive index of a Bruggeman nanoliquid, i.e. a solution consisting of spherical nanoparticles embedded into a host liquid such as water, using the maximum entropy method. This retrieval can be immediately performed once the optical properties of the host liquid are known. In this paper we investigate the upper limit of the volume fraction of spherical nanoparticles in a solution that still yields a reliable result in the retrieval based on the maximum entropy method. Finally, we show that by squeezing the spectrum we can significantly reduce the errors in the analysis and retrieve the effective complex refractive index for a high volume fraction of nanoparticles. ¶Permanent address: Department of Physics, University of Joensuu, PO Box 111, FI-80101 Joensuu, Finland. ∥Emails: erik.vartiainen@lut.fi (EMV); kai.peiponen@joensuu.fi (K-EP)