Fig. 3

Relationship of PV-ATM data to vibrational absorbance for sucrose. The measured Δabs(ν,θ) using (a) far-field orientation dependent absorption, b near field anisotropic absorbance (ATM), and c PV-ATM. The THz radiation polarized in the a-b plane and the 0° orientation corresponds to the THz polarization parallel to the a axis. Also shown is simulation of the PV-ATM measurement (d). The simulations indicate that the increased structure in the PV-ATM spectra compared to anisotropic absorption arises from sensitivity to both the resonant anisotropic birefringence and the EO detector crystal polarization dependence