14 September 1994 One kind of error in modulational polarimetry
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In laboratory and astronomical polarimetry it is often still customary to employ sinusoidal voltages to control electro-optical modulators. In this case, signals on the main and double frequencies are usually recorded. Control voltages are reasonably high, up to 2 divided by 5 thousand volts, when using crystals like ADP, KDP, KD*P, and of some other types. Obviously, with so high values, nonlinear distortions of control voltages of up to 5 divided by 7% are almost unavoidable. In this paper, in a rather concise form, it is shown that nonlinear distortions of control voltage provide the source for spurious signals. A simple analytical expression is obtained, which relates the spurious signal amplitude to the amount of nonlinear distortions of modulating voltage. By examining a numerical example, it follows in particular that in some cases this factor is able to restrict the sensitivity of circular polarization measurements to 10-3 divided by 10-4. The aforesaid applies also for many objective polarimeters designed for measuring the rotation of the linear polarization plane.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Nikolai I. Kobanov, "One kind of error in modulational polarimetry", Proc. SPIE 2265, Polarization Analysis and Measurement II, (14 September 1994); doi: 10.1117/12.186686; https://doi.org/10.1117/12.186686


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