Analysis of performance of three- and five-stack achromatic half-wave plates at millimeter wavelengths

TL;DR

This paper evaluates the performance of three- and five-stack achromatic half-wave plates at millimeter wavelengths, focusing on polarization measurement accuracy, systematic errors, and optimal alignment for high efficiency.

Contribution

It provides a detailed analysis of how construction parameters and incident spectrum affect AHWP performance, offering guidelines for optimal alignment and systematic error mitigation.

Findings

High modulation efficiency achievable with few-degree plate alignment

Phase offset depends on incident spectrum and stack configuration

Systematic errors can be minimized with proper calibration

Abstract

We study the performance of achromatic half-wave plates (AHWP) as a function of their construction parameters, the detection bandwidth of a power detector operating in the millimeter wave band, and the spectral shape of the incident radiation. We focus particular attention on the extraction of the degree of incident polarization and its orientation angle from the intensity measured as a function of AHWP rotation angle, which we call the IVA (intensity versus angle). We quantify the phase offset of the IVA and point to potential systematic errors in the extraction of this offset in cases where the incident spectrum is not sufficiently well known. We show how the phase offset and modulation efficiency of the AHWP depend on the relative angles between the plates in the stack and find that high modulation efficiency can be achieved with alignment accuracy of few degrees.