Far-IR Ellipsometer at

U4IR beamline,



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Project Description

About the Project

In 2008-2010 we developed a far-IR spectroscopic ellipsometer at the U4IR beamline of the National Synchrotron Light Source (NSLS) in Brookhaven National Laboratory (BNL). This ellipsometer is capable to measure a full-Mueller matrix Mij of the sample by adopting the Hauge’s method using rotating compensators and rotating wire-grid linear polarizers. We utilize exceptional brightness of synchrotron radiation in the broad spectral range between 10 and 4,000 cm-1. Fourier-transform infrared (FT-IR) spectrometer is used for multi-wavelength data acquisition. The sample stage has temperature variation between 4.2 and 450 K, wide range of q-2q rotation, c angle adjustment, and X-Y-Z translation.  The Labview software controls the motors, temperature controller, and spectrometer, and allows automated experiments with the pre-programmed measurement schedules. Data analysis is based on the Berreman’s 4×4 propagation matrix formalism to calculate the Mueller matrix parameters of anisotropic samples with magnetic permittivity µ≠1. Non-linear regression of the Mueller matrix spectra acquired at variable incidence angles and sample orientations, allows extraction of dielectric constant and magnetic permittivity tensors for bulk and thin-film samples across the broad far-IR spectral range. Applications of this ellipsometer system for multiferroic materials: anisotropic single crystals and thin films with µ≠1 is the main focus of our present activity. 

This development effort has been supported by NSF-MRI-0821224.

Muller Matrix Ellipsometer Project

at  U4IR beamline NSLS-BNL