Polarization angle accuracy for future CMB experiments. The COSMOCal project and its prototype in the 1mm band

The Cosmic Microwave Background (CMB) radiation offers a unique window into the early Universe, facilitating precise examinations of fundamental cosmological theories. However, the quest for detecting B-modes in the CMB, predicted by theoretical models of inflation, faces substantial challenges in terms of calibration and foreground modeling. The COSMOCal (COsmic Survey of Millimeter wavelengths Objects for CMB experiments Calibration) project aims at enhancing the accuracy of the absolute calibration of the polarization angle $\psi$ of current and future CMB experiments. The concept includes the build of a very well known artificial source emitting in the frequency range [20-350] GHz that would act as an absolute calibrator for several polarization facilities on Earth. A feasibility study to place the artificial source in geostationary orbit, in the far field for all the telescopes on Earth, is ongoing. In the meanwhile ongoing hardware work is dedicated to build a prototype to test the technology, the precision and the stability of the polarization recovering in the 1 mm band (220-300 GHz). High-resolution experiments as the NIKA2 camera at the IRAM 30m telescope will be deployed for such use. Once carefully calibrated ($\Delta\psi$ < 0.1 degrees) it will be used to observe astrophysical sources such as the Crab nebula, which is the best candidate in the sky for the absolute calibration of CMB experiments.Comment: to appear in Proc. of the mm Universe 2023 conference, Grenoble (France), June 2023, published by F. Mayet et al. (Eds), EPJ Web of conferences, EDP Science

Enhancing heterodyne system performances using fundamental millimeter wave mixers with 36 GHz instantaneous IF Bandwidth and 35 % relative detection bandwidth

International audienceThe development of low noise and wide instantaneous IF and RF bandwidth fundamental mixers is reported. The proposed architecture offers attractive potential for ultra-large bandwidth and fast data rates wireless links. Moreover, it could be used to either reduce total power radiometer sensitivity or to enhance large scale mapping heterodyne systems for atmospheric science instruments

Demonstration of a 25% bandwidth 520-680 GHz Schottky receiver front-end for planetary science and remote sensing

International audiencePlanetary atmospheres are rich in molecular species with spectral rotational and vibrational signatures in the millimeter and submillimeter frequency range. In particular, the 520-680 GHz frequency ranges offers access to a various amount of minor and major constituents of the atmosphere, including water vapour (H2O), carbon monoxide (CO), hydrogen cyanide (HCN), carbon monosulfide (CS) and their isotopes to derive temperature and wind velocities [1] or surface emissivity [2]. Recently, we have developed and manufactured the 560 GHz subharmonic mixer, showing the excellent performances in the 525-625 GHz frequency region with mixer noise temperature of about 870 K, around 30hf/kB [3]. In this paper we present an update and extensive measurement showing that the mixer's RF bandwidth can be extended up to 25% keeping the excellent performances. Assessment study of the radiometer modelling and Schottky junction parameter deviations will be presented. A best fit of the junction I/V allows to derive the main diode DC parameters retrofitted to analytical models such as [4]. We discuss efforts on implementation of large bandwidth receiver system, including solutions for local power across large bandwidth [5] or in complex systems using simultaneous molecular line observations [6]

GaN Schottky Diode for High Power THz Generation using Multiplier Principle

International audienceGaN-based planar Schottky barrier diodes with potential applications in THz frequency multipliers were fabricated and characterized. GaN is a promising candidate to overcome all the physical limitations of GaAs which have been reached in the frame of high frequency power multiplier applications. Fabrication process of GaN Schottky diodes performed by e-beam is presented and DC characterizations are reported. The preliminary results showed that the behaviour in reverse bias is dominated by a leakage coming from the Schottky surface more than the periphery of the diode despite the supposed damage caused by the dry etching

Development Status of Millimeter Wave GaN Schottky Doublers above W-band for the Implementation of European Terahertz Sources for Astronomy and Astrophysics

International audienceIn this report we present the effort to develop high power handling and efficiency GaN-based frequency doublers required to build a 1 THz local oscillator source for instrumentation in astronomy and astrophysics. The design study focuses on identifying the key aspect to reach performances with simplified architecture as compared to existing solutions. Predicted performances of GaN Schottky doublers are presented and discussed. A single section doubler produces an output power of 175 mW at 114 GHz for an input power of 1 W. The reverse bias voltage is tuned to maximize its performance but remains well below the breakdown voltage of the GaN Schottky diodes developed at IEMN (-75 V). Its performance can be enhanced further with thin epilayer and high mobility sample for the diode development and the state-of-theart performance can be achieved by using power combining technique to reach the 300 mW goals