Error calibration method for a vortex retarder based spatially modulated polarimeter

The vortex retarder based spatially modulated polarimeter provides a promising polarization measurement technique with rapidness, compactness, simplicity and stability. However, such a technique faces the challenging problem of calibration that has not yet been addressed, which significantly constrains its potential broad ap-plications. In this paper, we study the total effects of different error sources that limit the measurement precision of the vortex retarder based spatially modulated polarimeter, and propose an efficient calibration method to reduce the errors. A theoretical model is established to analyze the general effects of the different error sources on the intensity modulation curve of the incident waves with the Stokes-Mueller formalism. It is revealed that the error of the intensity modulation curve of any incident beam can be calculated, simply through those error curves of the beams polarized at 0 and 45 degrees. Calibration experiments of incident beams with different polarization di-rections are presented, verifying that our proposed method is efficient, accurate and easy to implement. More-over, our approach can effectively reduce the Stokes parameters' measurement error from about 0.05 to <0.01, which is superior to several typical commercial polarimeters.