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Compensating for nonlinear dispersion in channeled spectropolarimetry
Applied Optics
|June 17, 2020
Summary
Magnesium fluoride (MgF2) waveplates minimize nonlinear dispersion errors in channeled spectropolarimeters. This study quantifies these errors and finds MgF2 offers superior performance, reducing crosstalk in polarization data acquisition.
Area of Science:
- Optics and Photonics
- Polarimetry
- Spectroscopy
Background:
- Common waveplate materials cause nonlinear dispersion of retardance.
- This nonlinearity creates unwanted chirp in interference fringes used in channeled spectropolarimeters.
- This chirp complicates heterodyning polarization data.
Purpose of the Study:
- To quantify the nonlinearity of retardance in common waveplate materials.
- To identify waveplate materials with lower nonlinearity.
- To analyze and minimize crosstalk errors caused by dispersion nonlinearity.
Main Methods:
- Quantification of nonlinear dispersion of retardance.
- Survey and comparison of common waveplate materials (e.g., MgF2).
- Analysis of crosstalk dependence on phase calibration sequence and implementation.
Main Results:
- MgF2 exhibits significantly lower nonlinearity compared to other materials.
- Dispersion nonlinearity causes crosstalk, which is sequence-dependent.
- Shifting channels to baseband before windowing minimizes crosstalk error.
Conclusions:
- MgF2 is a preferred material for waveplates in spectropolarimetry due to low nonlinearity.
- Understanding and mitigating dispersion nonlinearity is crucial for accurate polarization data.
- Optimized data processing, including baseband shifting, reduces crosstalk and improves measurement fidelity.
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