  In recent years, handheld and portable terahertz instruments have been in
rapid development for various applications ranging from non-destructive testing
to biomedical imaging and sensing. For instance, we have deployed our Portable
Handheld Spectral Reflection (PHASR) Scanners for in vivo full-spectroscopic
imaging of skin burns in large animal models in operating room settings. In
this paper, we debut the polarimetric version of the PHASR Scanner, and
describe a generalized calibration technique to map the spatial and spectral
dependence of the Jones matrix of an imaging scanner across its field of view.
Our design is based on placement of two orthogonal photoconductive antenna
(PCA) detectors separated by a polarizing beam splitter in the PHASR Scanner
housing. We show that at least three independent measurements of a
well-characterized polarimetric calibration target are sufficient to determine
the polarization state of the incident beam at the sample location, as well as
to extract the Jones propagation matrix from the sample location to the
detectors. We have tested the accuracy of our scanner by validating
polarimetric measurements obtained from a birefringent crystal rotated to
various angles, as compared to the theoretically predicted response of the
sample. This new version of our PHASR scanner can be used for high-speed
imaging and investigation of heterogeneity of polarization-sensitive samples in
the field.
