Two-color approach for determination of thickness and dielectric constant of thin films using surface plasmon resonance spectroscopy

We report a real time, in situ non-perturbative all-optical approach for determining both the average thickness and the average dielectric constant of transparent thin films using surface plasmon resonance spectroscopy. While it is impossible to obtain both of these parameters from a single surface plasmon resonance spectroscopy experiment, we show both theoretically and experimentally that a two-color experiment allows unambiguous determination of both parameters. The approach is tested for organic thin films at the gold/solution interface which have thickness of a single monolayer.