Fig. 3: Applicability of the different ellipsometric models.

a Comparison of the measured and modeled ellipsometric data. Dotted curves belong to the single layer model, where the appearing distinct peaks provide a clear indication that this simple model is not able to describe the measured changes sufficiently. Solid curves with no modulation belong to the two-layer model, which reproduces perfectly the measurements. b Temperature of the thin film hosting the SPPs as a function of laser power applied for SPP excitation. Gray squares, black diamonds, dark blue circles and red triangles represent the temperature originating from temperature calculations, from reflectivity measurements, from the ellipsometric model considering a single layer with elevated temperature, and from the ellipsometric model considering two layers, respectively. Error bars of the temperature calculations are defined by the uncertainties of the power converted to SPP excitation; for reflectivity measurements, the uncertainty of C parameter was taken into account; while for the ellipsometric results, error bars originate from thickness uncertainties (standard deviations of the deduced results in all cases).