Optimization of a Microwave Polarimeter for Astronomy with Optical Correlation and Detection

Cosmic Microwave Background (CMB) B-modes detection is the main focus of future CMB experiments because of the valuable information it contains, particularly to probe the physics of the very early universe. For this reason, we have developed an optimized polarimeter demonstrator sensitive to the 10-20 GHz band in which the signal received by each antenna is modulated into a Near Infrared (NIR) laser by a Mach-Zehnder modulator. Then, these modulated signals are optically correlated and detected using photonic back-end modules consisting of voltage-controlled phase shifters, a 90-degree optical hybrid, a pair of lenses, and an NIR camera. During laboratory tests, a 1/f-like noise signal related to the low phase stability of the demonstrator has been found experimentally. To solve this issue, we have developed a calibration method that allows us to remove this noise in an actual experiment, until obtaining the required accuracy level in the measurement of polarization.

Automated summary

The detection of Cosmic Microwave Background (CMB) B-modes is crucial for future CMB experiments as it provides valuable information about the physics of the early universe. To achieve this, an optimized polarimeter demonstrator was developed to be sensitive to the 10-20 GHz band. The demonstrator modulates the received signals into Near Infrared (NIR) laser, optically correlates them, and uses photonic back-end modules for detection. The issue of low phase stability was addressed with a calibration method to remove the related 1/f-like noise signal.