Hyperspectral mapping of anisotropy

Anisotropy of absorbance (dichroism) and birefringence limits spatial resolution, sensitivity during quantitative detection of trace analytes, as well as spectral imaging in the near-IR and mid-IR spectral ranges. Here we show hyperspectral imaging capable of determining retardance and absorbance due to small changes in the real and imaginary parts of the refractive index ∼Δ n and ∼Δ κ at each single point of a measurement at diffraction limited resolution. This single-beam technique allows the retrieval of the phase and amplitude information by virtue of a twice different angular dependence of Δ n and Δ κ on the sample orientation angle. It has potential applications in analytical science, multi-dimensional optical memory devices, and forensic/defense/sensor fields. Hyperspectral imaging is now augmented by separation of the birefringence, dichroism and orientation function at the same wavelength and pixel by combining Malus and Beer-Lambert laws.