Scientific verification of Faraday Rotation Modulators: Detection of diffuse polarized Galactic emission

TL;DR

This paper verifies the effectiveness of Faraday Rotation Modulators in detecting diffuse polarized Galactic emission at millimeter wavelengths, demonstrating high signal-to-noise detection and agreement with models.

Contribution

It provides the first high signal-to-noise detection of celestial polarization using active optical modulation with FRMs in the mm-wave range.

Findings

Successful detection of Galactic polarization with FRMs

Strong agreement with existing polarization models

First demonstration of high S/N celestial polarization detection using active modulators

Abstract

The design and performance of a wide bandwidth linear polarization modulator based on the Faraday effect is described. Faraday Rotation Modulators (FRMs) are solid-state polarization switches that are capable of modulation up to ~10 kHz. Six FRMs were utilized during the 2006 observing season in the Background Imaging of Cosmic Extragalactic Polarization (BICEP) experiment; three FRMs were used at each of BICEP's 100 and 150 GHz frequency bands. The technology was verified through high signal-to-noise detection of Galactic polarization using two of the six FRMs during four observing runs in 2006. The features exhibit strong agreement with BICEP's measurements of the Galaxy using non-FRM pixels and with the Galactic polarization models. This marks the first detection of high signal-to-noise mm-wave celestial polarization using fast, active optical modulation. The performance of the FRMs during periods when they were not modulated was also analyzed and compared to results from BICEP's 43 pixels without FRMs.