Polarization purity and cross-channel intensity correlations.

作者：Daniel Kestner, Alexander Kostinski · 发表于：Journal of The Optical Society of America A-optics Image Science and Vision · 年份：2025 · DOI：10.1364/josaa.564696 · 研究领域：Medicine

We consider the question of monitoring polarization purity, that is, measuring deviations from orthogonality δτ and δϵ of an ostensibly orthogonal polarization basis with a reference channel of ellipticity ϵ and tilt τ. A simple result was recently derived for a phase-sensitive receiver observing unpolarized radiation [IEEE Trans. Geosci. Remote Sens.62, 2003610 (2024)10.1109/TGRS.2024.3380531]: with ρ(1) denoting the Pearson complex correlation coefficient between channel complex fields, it states that ∓cos⁡(2ϵ)δτ±iδϵ≈ρ(1) when δτ,ϵ≪1. However, phase-sensitive (in-phase and quadrature) data are seldom available at optical frequencies. To that end, here we generalize the result by deriving a new equation for the polarization "alignment" error: cos2(2ϵ)δτ2+δϵ2≈ρ(2), where ρ(2) is the intensity cross-correlation coefficient. Only the measurement of the (real) intensity cross-correlation coefficient is needed when observing unpolarized light. For the special case of a linearly polarized basis, the tilt error is simply δτ≈ρ(2), and for the circular basis case, with ellipticity deviation δϵ from circular helicity π/4 (the reference channel of opposite helicity), δϵ≈ρ(2). These results provide simple means to gauge the quality of polarimeters and depolarizers.