We implemented a polarization modulation technique1 to measure polarization rotation and ellipticity of a light beam with a resolution as high as <0.001°. The experimental setup covers an exceptionally broad energy range (0.07 eV – 7 eV) combining a grating monochromator (Oriel Cornerstone) and a Fourier transform spectrometer (Varian 670 FT-IR). The NIR-VIS light path (0.5 eV – 6.2 eV) based on the grating spectrometer is equipped with a fused silica PEM and fused silica / CaF2 optical elements, while in infrared region (0.08 eV – 1.0 eV) a ZnSe PEM modulates the polarization and off-axis parabolic mirrors and ZnSe lenses guide the light beam.
In order to cover such wide spectral range several detectors are used: a photomultiplier, an InGaAs photodiode, an InSb photodiode and a MCT photoconductive detector. The spectral resolution of the grating spectrometer can be better than 2 nm, while the resolution of the infrared setup is 1 cm-1. Low temperature experiments, from room temperature down to 5 K, can be performed in an optical cryostat which is equipped with permanent magnets providing magnetic fields up to ±0.4T.
This spectrometer system is also capable of performing reflectivity, absorption, linear and circular dichroism measurements.