On the emissivity of wire-grid polarizers for astronomical observations at mm-wavelengths

TL;DR

This paper measures the emissivity of metallic wire-grid polarizers at mm-wavelengths, highlighting their low emissivity and suitability for sensitive astronomical observations like CMB studies.

Contribution

It provides empirical measurements of wire-grid emissivity and discusses their implications for low-background astronomical instruments.

Findings

Wire-grid emissivity is a few percent, varying with fabrication and aging.

Effective emissivity impacts the performance of polarimeters in astronomy.

Wire-grids are suitable for low-background applications like CMB observations.

Abstract

We have measured, using a custom setup, the emissivity of metallic wire-grids, suitable for polarimeters and interferometers at mm and far infrared wavelengths. We find that the effective emissivity of these devices is of the order of a few %, depending on fabrication technology and aging. We discuss their use in astronomical instruments, with special attention to Martin Puplett Interferometers in low-background applications, like astronomical observations of the Cosmic Microwave Background.