Polarimetrii

Polarimetrii, the Romanian term for polarimetry, is a branch of optics concerned with the measurement and interpretation of the polarization state of light and its alteration by materials and surfaces. Polarization describes the orientation and time-varying behavior of the electric field; a light beam can be described by the Stokes parameters or equivalent representations such as the Poincaré sphere. Polarimetrii includes the design of instruments to determine polarization states (polarimeters) and to quantify how an object changes polarization (for example, through birefringence, dichroism, or scattering).

Common measurement approaches use polarizers, waveplates, and polarization analyzers to determine the Stokes vector, or employ Mueller calculus to model the effect of optical elements. Techniques span direct polarimetry, ellipsometry (measurements of complex refractive index and film thickness from polarization changes upon reflection), and spectropolarimetry that records polarization as a function of wavelength. Modern instruments often use polarization modulators (photoelastic modulators, electro-optic modulators) and fast detectors to achieve high accuracy and mapping capability.

Applications are wide: astronomy and cosmology (inferring magnetic fields and scattering geometries), remote sensing and atmospheric science (aerosol and cloud properties), material science and engineering (stress analysis, thin-film characterization), chemistry and biology (characterization of chiral substances and biomolecules), and biomedical imaging (polarization-sensitive optical coherence tomography). Challenges include instrumental polarization, depolarization by scattering, calibration, and interpretation of complex polarization signals. Polarimetrii thus provides a quantitative framework for connecting light’s polarization with material properties and processes.