Anisotropy Studied by Polarization-Modulated Fourier Transform Infrared Reflection Difference Microspectroscopy

Abstract

We investigated anisotropic optical behavior in solid-state materials using Fourier transform infrared reflection microspectroscopy in combination with polarization modulation. For a Ca_1.8Sr_0.2RuO₄ crystal with an isotropic optical surface, we found the reflection difference to be very close to zero, independent of the azimuthal angle of the sample. A Ca_1.4Sr_0.6RuO₄ crystal with an anisotropic optical surface, however, exhibited a large anisotropic optical response with a strong angular dependence following a sinusoidal behavior. Furthermore, we examined the spatial distribution of the reflection difference in Bi_0.17Ca_0.83MnO_3+δ using infrared synchrotron radiation and could clearly distinguish microscopic anisotropic domains having different optical axes. These results demonstrate that our experimental scheme can be used as a powerful tool to spectrally and spatially resolve anisotropy of solid-state materials in the mid-infrared region.