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14 pages, 2021 KiB

Open AccessArticle

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

by Guillermo Pascual-Cisneros, Francisco J. Casas and Patricio Vielva

Sensors 2023, 23(5), 2414; https://doi.org/10.3390/s23052414 - 22 Feb 2023

Cited by 3 | Viewed by 1659

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. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 4465 KiB

Open AccessArticle

Calibration of a Polarimetric Microwave Radiometer Using a Double Directional Coupler

by Luisa de la Fuente, Beatriz Aja, Enrique Villa and Eduardo Artal

Remote Sens. 2021, 13(11), 2109; https://doi.org/10.3390/rs13112109 - 27 May 2021

Cited by 3 | Viewed by 2615

Abstract

This paper presents a built-in calibration procedure of a 10-to-20 GHz polarimeter aimed at measuring the I, Q, U Stokes parameters of cosmic microwave background (CMB) radiation. A full-band square waveguide double directional coupler, mounted in the antenna-feed system, is used to inject differently polarized reference waves. A brief description of the polarimetric microwave radiometer and the system calibration injector is also reported. A fully polarimetric calibration is also possible using the designed double directional coupler, although the presented calibration method in this paper is proposed to obtain three of the four Stokes parameters with the introduced microwave receiver, since V parameter is expected to be zero for the CMB radiation. Experimental results are presented for linearly polarized input waves in order to validate the built-in calibration system. Full article

(This article belongs to the Special Issue New Technologies for Earth Remote Sensing)

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13 pages, 910 KiB

Open AccessReview

An SU(2) Gauge Principle for the Cosmic Microwave Background: Perspectives on the Dark Sector of the Cosmological Model

by Ralf Hofmann

Universe 2020, 6(9), 135; https://doi.org/10.3390/universe6090135 - 24 Aug 2020

Cited by 6 | Viewed by 3522

Abstract

We review consequences for the radiation and dark sectors of the cosmological model arising from the postulate that the Cosmic Microwave Background (CMB) is governed by an SU(2) rather than a U(1) gauge principle. We also speculate on the possibility of actively assisted structure formation due to the de-percolation of lump-like configurations of condensed ultralight axions with a Peccei–Quinn scale comparable to the Planck mass. The chiral-anomaly induced potential of the axion condensate receives contributions from SU(2)/SU(3) Yang–Mills factors of hierarchically separated scales which act in a screened (reduced) way in confining phases. Full article

(This article belongs to the Special Issue Shedding Light to the Dark Sides of the Universe: Cosmology from Strong Interactions)

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17 pages, 4548 KiB

Open AccessArticle

A Microwave Polarimeter Demonstrator for Astronomy with Near-Infra-Red Up-Conversion for Optical Correlation and Detection

by Francisco J. Casas, David Ortiz, Beatriz Aja, Luisa de la Fuente, Eduardo Artal, Rubén Ruiz and Jesús M. Mirapeix

Sensors 2019, 19(8), 1870; https://doi.org/10.3390/s19081870 - 19 Apr 2019

Cited by 7 | Viewed by 3292

Abstract

This paper presents a 10 to 20 GHz bandwidth microwave polarimeter demonstrator, based on the implementation of a near-infra-red frequency up-conversion stage that allows both the optical correlation, when operating as a synthesized-image interferometer, and signal detection, when operating as a direct-image instrument. The proposed idea is oriented towards the implementation of ultra-sensitive instruments presenting several dozens or even thousands of microwave receivers operating in the lowest bands of the cosmic microwave background. In this work, an electro-optical back-end module replaces the usual microwave detection stage with Mach–Zehnder modulators for the frequency up-conversion, and an optical stage for the signals correlation and detection at near-infra-red wavelengths (1550 nm). As interferometer, the instrument is able to correlate the signals of large-format instruments, while operating as a direct imaging instrument also presents advantages in terms of the possibility of implementing the optical back end by means of photonic integrated circuits to achieve reductions in cost, weight, size, and power consumption. A linearly polarized input wave, with a variable polar angle, is used as a signal source for laboratory tests. The receiver demonstrator has proved its capabilities of being used as a new microwave-photonic polarimeter for the study of the lowest bands of cosmic microwave background. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 2735 KiB

Open AccessArticle

The Thirty Gigahertz Instrument Receiver for the QUIJOTE Experiment: Preliminary Polarization Measurements and Systematic-Error Analysis

by Francisco J. Casas, David Ortiz, Enrique Villa, Juan L. Cano, Jaime Cagigas, Ana R. Pérez, Beatriz Aja, J. Vicente Terán, Luisa De la Fuente, Eduardo Artal, Roger Hoyland and Ricardo Génova-Santos

Sensors 2015, 15(8), 19124-19139; https://doi.org/10.3390/s150819124 - 5 Aug 2015

Cited by 6 | Viewed by 4895

Abstract

This paper presents preliminary polarization measurements and systematic-error characterization of the Thirty Gigahertz Instrument receiver developed for the QUIJOTE experiment. The instrument has been designed to measure the polarization of Cosmic Microwave Background radiation from the sky, obtaining the Q, U, and I Stokes parameters of the incoming signal simultaneously. Two kinds of linearly polarized input signals have been used as excitations in the polarimeter measurement tests in the laboratory; these show consistent results in terms of the Stokes parameters obtained. A measurement-based systematic-error characterization technique has been used in order to determine the possible sources of instrumental errors and to assist in the polarimeter calibration process. Full article

(This article belongs to the Section Physical Sensors)

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