We report an original method for directly fabricating gold nanoparticles (Au NPs) in a polymer matrix using a thermal treatment technique and theoretically and experimentally investigate their plasmonic properties. The polymeric-metallic nanocomposite samples were first prepared by simply mixing SU-8 resist and Au salt with different concentrations. The Au NPs growth was triggered inside the polymer through a thermal process on a hot plate and in air environment. The Au NPs creation was confirmed by the color of the nanocomposite thin films and by absorption spectra measurements. The Au NPs sizes and distributions were confirmed by transmission electron microscope measurements. It was found that the concentrations of Au salt and the annealing temperatures and durations are all crucial for tuning the Au NPs sizes and distributions, and, thus, their optical properties. We also propose a simulation model for calculations of Au NPs plasmonic properties inside a polymer medium. We realized that Au NPs having large sizes (50 to 100 nm) play an important role in absorption spectra measurements, as compared to the contribution of small NPs (<20 nm), even if the relative amount of big Au NPs is small. This simple, low-cost, and highly reproducible technique allows us to obtain plasmonic NPs within polymer thin films on a large scale, which can be potentially applied to many fields.

We study dynamical Newton-ring like fringes created by interfering Fresnel reflections of an evaporating sessile liquid droplet, which acts as a miniature convex lens. We show that conventional thin-film interference theory cannot be applied to explain the physical phenomenon. Because of the large thickness and curvature of the liquid droplet, the geometrical light paths of the reflected beams become very complicated and can no longer be considered approximately collimated. This results in interference fringes of concentric circles with different directional motion depending on the observation plane. The change in the interference pattern as a function of time is demonstrated by both simulation and experiment. This investigation allows us to fully understand the formation of interference patterns of an optical system having arbitrary thickness and curvature. In addition, by analyzing the high-contrast dynamic rings, we demonstrate nanoscale sensitivity to surface height changes of an evaporating water drop.