Accuracy Limits of Polarization-Independent Optical Depolarizers Based on Rotating Waveplates

TL;DR

This paper investigates the fundamental accuracy limits of polarization-independent optical depolarizers built from cascaded rotating waveplates, analyzing how retardation errors affect residual polarization.

Contribution

It provides a detailed analysis of how waveplate sequence and rotation frequency impact depolarizer accuracy, highlighting the benefits of using multiple waveplates.

Findings

Residual degree-of-polarization is proportional to retardation error with one waveplate.

Adding more waveplates reduces residual DOP to the square of the retardation error.

Optimal waveplate sequences enable fast and accurate depolarization.

Abstract

Optical depolarizers for monochromatic waves which work independent of input polarization can be built from cascaded electrooptic rotating waveplates. If the waveplate retardations deviate from their desired values then the worst-case residual degree-of-polarization DOPmax is larger than its desired value 0. In a depolarizer consisting of one rotating halfwave and one rotating quarterwave plate, DOPmax roughly equals the retardation error, which is <<1. However, with just one rotating quarterwave plate more, DOPmax roughly equals the square of the retardation error which is a much smaller value. Thereby depolarizer accuracy is substantially improved. Waveplate sequence and rotation frequency combinations suitable for fast depolarization are discussed.