Ultra broadband phase measurements on nanostructured metasurfaces

We report on an interferometric method developed for ultra broadband (from lambda = 0.65 mu m to lambda = 1.7 mu m) phase measurements on metasurfaces in transmission and reflection. Due to a unique performance of our method in terms of the accessible spectral range, accuracy (+/- 0.02 rad), and flexibility with respect to the sample arrangement, this technique can be broadly used as a versatile tool for the comprehensive characterization of a broad class of dispersive optical materials. We compare our experimental technique with an indirect approach and based on the Kramers-Kronig transformation analysis, establish a rule for the use of the indirect method. (C) 2014 AIP Publishing LLC.