Terahertz multispectral polarimetric imaging based on intensity measurement

A compact terahertz (THz) polarimetric spectrometer and imaging system is demonstrated using polarization-sensitive frequency-selective surfaces (PS-FSS) and rapid, intensity-based detection. Real-time Stokes parameter extraction enables angle-of-linear-polarization (AoLP) measurements and quantitative retrieval of the birefringence of a 1-mm-thick x-cut quartz crystal, used here as a benchmark anisotropic sample. The extracted birefringence is in good agreement with THz time domain spectroscopy-based measurements, validating the accuracy of the proposed THz polarimetric approach. Signal-to-noise ratios (SNR) up to 87 dB across 0.23-0.41 THz ensure reliable discrimination of the measured spectral components above the noise floor. Extending this approach to raster-scanned THz imaging using distinct PS-FSS orientations (0{\deg}, 45{\deg}, 90{\deg}, and 135{\deg}) enables simultaneous mapping of frequency-dependent Stokes parameters. The resulting degree of linear polarization (DoLP) and AoLP maps exhibit well-resolved polarimetric contrast, consistent with numerical simulations and independent visible polarimetric measurements. Operating entirely without field-resolved detection or mechanical delay stages, the system provides a robust and compact platform for THz polarimetric spectroscopy and imaging of anisotropic materials.