Group Delay Dispersion Measurements on Mid-Infrared Supermirrors

Methods and results for broadband group delay dispersion measurements of monocrystalline and amorphous-crystalline hybrid supermirrors, as well as an all-amorphous mirror, are presented. Measurements are performed with a custom-built white light interferometer covering a spectral range from 2.5 to 4.8 (Formula presented.), capable of measuring in both balanced and unbalanced measurement configuration. The results are compared with theoretical transfer-matrix method simulations and an independent measurement using a commercial Fourier-transform infrared spectrometer. Additionally, group delay dispersion is investigated by direct differentiation using a local polynomial smoothing approach (Savitzky-Golay filter), and strong consistency is observed between the measurement results, the theoretical prediction, and the estimation using this method.