Spectrally modulated polarimetry with wavelength domain analysis.

Spectrally modulated Stokes polarimeters use a pair of high-order crystal retarders to generate a spectrally dependent modulation of the polarization of light. In these systems, the detected intensity versus wavenumber spectrum is usually referred to as a channeled spectrum, and the Fourier inversion of this spectrum allows the determination of Stokes parameters of light without needing any other mechanical or active device for polarization control. This work proposes a spectrally modulated polarimeter beyond the concept of a channeled wavenumber spectrum, so effectively detaching the spectral modulation from the Fourier analysis technique. The wavelength domain analysis we use is best suited for dispersive spectrometers offering intensity versus wavelength measurements. The technique is illustrated with the measurement of very small optical rotations produced by sucrose solutions. The proposed technique is easily extendable to spectrally modulated Mueller polarimeters.

Error analysis of channeled Stokes polarimeters.

This work presents an analysis of passive polarimeters with spectral channeling, referred to as Stokes channeled spectropolarimeters (SCS). The SCS setup comprises two thick birefringent retarders, followed by a horizontal linear polarizer. The simulation of these polarimeters and two extraction methods for the incident Stokes vector is presented as well. The effects of different retarders thickness ratios, the global retardance factor, retardance errors, axes alignment error, and Gaussian noise on root mean square (RMS) errors of the recovered Stokes parameters are described. Furthermore, two different, previously published data extraction methods are presented and compared. We found the best polarimeter configurations from the cases studied, and our results suggest that a mixed extraction process, using different extraction methods for different Stokes parameters, could give better results by reducing RMS errors by about a factor of 5. It is worth mentioning that although calibration is needed to account for the effect of errors, this is out of the scope of this work.

Analysis of experimental errors in Mueller matrix channeled polarimeters.

This work analyzes the effect of experimental errors and measurement noise on Mueller matrix channeled spectropolarimeters. The main advantage of this type of polarimeter is the independence on temporal resolution, as it can be used as a snapshot polarimeter. The simulation of the polarimeters with experimental errors and two published extraction methods of the sample Mueller matrix are also presented. The Mueller matrix channeled spectropolarimeter (MMCS) setup consists of a mirrored Stokes channeled spectropolarimeter (SCS) as the polarization states generator (PSG) and a SCS as the polarization states analyzer (PSA). The SCS setup comprises two thick birefringent retarders followed by a horizontal linear polarizer. The effects of the thickness ratio of the retarders, the global retardance factor, retardance errors, axes alignment errors, and additive Gaussian noise are further studied to optimize the MMCS setups. In this work, we do not include a calibration procedure to improve the measured Mueller matrix parameters, but we study the sensitivity of the polarimeter to different configurations and error sources.