Heterogeneity and Birefringence of Soft Tissues Probed by the Polarization‐Sensitive Terahertz Solid Immersion Microscopy

ABSTRACT The polarization‐sensitive THz solid immersion (SI) microscope is applied to quantify the heterogeneity and birefringence of freshly‐excised rat tissues: the abdominal and tongue muscles, tendons of the flexor digitorum and extensor digitorum of the forelimb, Achilles tendon, abdominal aorta, and Corpus callosum of the brain. THz refractive indices of tissues are retrieved for the two orthogonal linear polarizations of the incident beam, which are collinear and transverse toward the fibrous structures. The observed THz birefringence, as high as a few percent, is attributed to tissue morphology relying on the hematoxylin and eosin (H those should be accounted for when developing novel methods of THz biophotonics.