Phase-shifting interferometry-based Fourier transform channeled spectropolarimeter.

Channeled spectropolarimetry is a snapshot technique for measuring the spectral dependence of the state of polarization of light. However, it suffers from two major limitations, namely, its high sensitivity to environmental perturbations and its susceptibility to channel crosstalk. These limitations reduce the polarimetric reconstruction accuracy of the spectropolarimeter. A new calibration technique for channeled spectropolarimetry is presented that utilizes the concept of phase-shifting interferometry to accurately acquire and demodulate the retardation phase factors, thereby improving the accuracy of the Stokes data reconstruction as well as enabling more robust performance. The new technique also enables the acquisition of high-resolution intensity spectrum by adopting a dual-scan measurement technique for reducing crosstalk. Experimental results show that calibrations using phase-shifting interferometry yield higher data reconstruction accuracy as compared to the self-calibration technique.

Intrinsic coincident full-Stokes polarimeter using stacked organic photovoltaics.

An intrinsic coincident full-Stokes polarimeter is demonstrated by using strain-aligned polymer-based organic photovoltaics (OPVs) that can preferentially absorb certain polarized states of incident light. The photovoltaic-based polarimeter is capable of measuring four Stokes parameters by cascading four semitransparent OPVs in series along the same optical axis. This in-line polarimeter concept potentially ensures high temporal and spatial resolution with higher radiometric efficiency as compared to the existing polarimeter architecture. Two wave plates were incorporated into the system to modulate the S3 Stokes parameter so as to reduce the condition number of the measurement matrix and maximize the measured signal-to-noise ratio. Radiometric calibration was carried out to determine the measurement matrix. The polarimeter presented in this paper demonstrated an average RMS error of 0.84% for reconstructed Stokes vectors after normalized to S0. A theoretical analysis of the minimum condition number of the four-cell OPV design showed that for individually optimized OPV cells, a condition number of 2.4 is possible.

Intrinsic coincident linear polarimetry using stacked organic photovoltaics.

Polarimetry has widespread applications within atmospheric sensing, telecommunications, biomedical imaging, and target detection. Several existing methods of imaging polarimetry trade off the sensor's spatial resolution for polarimetric resolution, and often have some form of spatial registration error. To mitigate these issues, we have developed a system using oriented polymer-based organic photovoltaics (OPVs) that can preferentially absorb linearly polarized light. Additionally, the OPV cells can be made semitransparent, enabling multiple detectors to be cascaded along the same optical axis. Since each device performs a partial polarization measurement of the same incident beam, high temporal resolution is maintained with the potential for inherent spatial registration. In this paper, a Mueller matrix model of the stacked OPV design is provided. Based on this model, a calibration technique is developed and presented. This calibration technique and model are validated with experimental data, taken with a cascaded three cell OPV Stokes polarimeter, capable of measuring incident linear polarization states. Our results indicate polarization measurement error of 1.2% RMS and an average absolute radiometric accuracy of 2.2% for the demonstrated polarimeter.