National Synchrotron Light Source Lunch Time Seminar

We present the far-IR spectroscopic ellipsometer at U4IR beamline of the National Synchrotron Light Source (NSLS) in Brookhaven National Laboratory (BNL). This Ellipsometer is designed to measure a full-Mueller matrix of the sample by using compensators and wire-grid linear polarizers. With the exceptional brightness of synchrotron radiation and the Fourier-transform infrared (FT-IR) spectrometer, we measure ellipsometric data at multi-wavelengths between 10 and 4,000 cm-1. Studies of the phase transitions in multiferroic crystals are available using the close-cycle cryostat for temperatures between 4.2 K and 450 K. The wide range of -2 rotation, angle adjustment, and X-Y-Z translation of sample stage enables high accuracies in the alignment, calibration, and ellipsometric measurement. With the Labview program interface, the automated experiments with the pre-programmed measurement schedules are performed by controlling the motors, temperature, and FT-IR spectrometer. The ellipsometric data analysis is based on the Berreman’s 4×4 propagation matrix formalism to extract dielectric permittivity and magnetic permeability tensors for bulk and thin film samples from the Mueller matrix measured at variable incidence angles and sample orientations across the broad far-IR spectral range. Applications of this far-IR ellipsometry for multiferroic materials with ≠1 and for metamaterials with the negative index of refraction will be discussed. This development effort is supported by NSF-MRI-0821224.