Reflection Shifts in Gold Nanoparticles

Metal nanoparticles are widely researched for the fabrication of novel low cost and more energy efficient optoelectronic devices. Optical properties of metal nanoparticles are known to be different from their bulk counterparts. In this paper, with an appropriate modification of Drude model, I provide an improved dielectric function for gold nanoparticles which accounts for particle size as well as temperature effects. The model is consequently used to investigate Goos-Hanchen and Imbert-Fedorov reflection shifts of an oblique linearly polarized laser beam reflected from the nanoparticles in various temperatures. It is shown that the beam light can contribute both spatial and angular shifts depending on its state of polarity. The maximum shifts take place at grazing angles when the polarization of light is set at TM and 45°. Study of the light deviations' sensitivity to the temperature indicates that reflection shifts decrease linearly at higher temperatures except in angular out-of-plane shift Θ𝐼𝐹 . The trend is incremental for different nanoparticle size, keeping the distinct behavior of Θ𝐼𝐹 . Such results allow more accurate prediction of many optical phenomena involving nanoscaled gold and may serve as a delicate method to determine nanoparticles' size.