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In this paper, we present a study on the optimization of Au/Si surface-enhanced Raman scattering sensors for ultrasensitive chemical detection. Au/Si nanosensors are carried out at the wafer scale with a low-cost and quick fabrication method composed of an anisotropic reactive ion etching followed by an electron beam evaporation of a gold layer. For this investigation, the thickness of the gold layer varied from 10 to 50 nm, and thiophenol molecules were chosen as model molecules of which the concentration varied from 10 - 12 to 10 - 3  M. The studied optimization exploits the effect of the gold layer thickness on the detection limit of thiophenol molecules for a fixed geometry of Si nanopillar. For all the cases investigated here, detection limits between 9 × 10 - 12 and 3 × 10 - 8  M are experimentally found for the detection of thiophenol molecules with the Au/Si nanopillars. Moreover, the best detection limits are achieved with the thickest gold layer. Finally, a 3D FDTD-based numerical analysis confirmed the experimental results.

As part of the Q&U Bolometric Interferometer for Cosmology instrument targeting the cosmic microwave background primordial B-modes, two kilo-pixel focal planes have been designed for a NEP of ∼ 3 × 10 - 17 W Hz adapted for ground-based observations. Those pixels are transition edge sensors (TESs) made of voltage-biased NbSi thin films with a critical temperature T c ∼ 400 mK and TiV absorbing grids. The TESs are coupled to a time-domain multiplexed electronics based on superconducting quantum interference devices and an additional SiGe cryogenic integrated circuit which provides a second multiplexing stage. In this paper, we briefly discuss the instrumental context of a quarter of focal plane (a 256-TES sub-array). Then, we present its typical manufacturing process and first test results at cryogenic temperature.

The next generations of cosmic microwave background (CMB) instruments will be dedicated to the detection and characterisation of CMB B-modes. To measure this tiny signal, instruments need to control and minimise systematics. Signal modulation is one way to achieve such a control. New generation of focal planes will include the entire detection chain on chip. In this context, we present a superconducting coplanar switch driven by DC current. It consists of a superconducting micro-bridge which commutes between its on (superconducting) and off (normal metal) states, depending on the amplitude of the current injection. To be effective, we have to use a high normal state resistivity superconducting material with a gap frequency higher than the frequencies of operation (millimeter waves). Several measurements were made at low temperature on NbN and yielded very high resistivities. Preliminary results of components dc behavior is shown. Thanks to its low power consumption, fast modulation and low weight, this component is a perfect candidate for future CMB space missions.

As shown by the Planck mission (Planck Collaboration. Astronomy and astrophysics. arXiv1303.5071P, 2013 ), background limited bolometers in a space environment are very sensitive to high energy particles. In order to not degrade their sensitivity, it is necessary to reduce this unwanted signal. To achieve this goal, a good understanding of the detector’s thermal architecture is mandatory. To investigate this question, we used an α particle source in front of our niobium silicon (NbSi) alloy Transition edge sensors (TES). The number of time constants required to fit the data and the way these time constants behave as we change the bias power gave us a good insight on the TES thermal architecture. Indeed we expect a decrease of the detector time constant due to the electro-thermal feedback properties. We will first present some standard characterizations of NbSi TES using a simple thermal model and how they indicate the presence of multiple thermal decouplings. Then we will show the results of the α particles measurements and how we used them to build our thermal model for Complex Impedance fitting. All this work has been done for the QUBIC experiment, a B-modes instrument.

We have demonstrated in an earlier paper that LEKIDs can be used in a polarisation selective way in a filled array configuration. A polarised response can be achieved by means of thick Nb polarising grids lithographed on the rear side of a 300 microns silicon wafer, on which Al resonators have been previously patterned. In the most interesting scheme that we have investigated, a unit cell formed by 4 pixels (2 by 2) responds simultaneously to two orthogonal (cartesian) polarisation states. To assess the effectiveness of this detection scheme, we have fabricated a first generation of devices (9 small arrays, 20–25 pixels each, on a 4 ″ Silicon wafer) by using a double-sided mask aligner suitable for a precise positioning of the individual grids in correspondence of each resonator’s meander, for the different LEKID geometries. We describe here the realisation of these first devices. The construction of a dedicated polarimetric test bench is also described in this contribution, together with the first characterisation results. We consider this activity as a first and necessary step to evaluate the polarisation purity attainable with polarisation-sensitive pixels whose size is comparable to the wavelength. This is a fundamental information to drive further studies.

Q and U Bolometric Interferometer for Cosmology (QUBIC) is a Fizeau interferometer sensitive to linear polarisation, to be deployed at the Antarctic station of Dome C. This experiment in its final configuration will be operated at 97, 150 and 220 GHz and is intended to target CMB primordial B-modes in a multipole window 20 < ℓ < 150 . A sensitivity of r = 0.05 (95 % CL) can be reached by the first module alone, after 2 years of operation. Here we review in particular its working principles, and we show how the QUBIC interferometric configuration can be considered equivalent to a pupil-plane filtered imaging system. In this context, we show how our instrument can be self-calibrated. Finally, we conclude by showing an overview of the first dual-band module (150/220 GHz), which will serve also as a demonstrator for the subsequent units, and review the technological choices we made for each subsystem, with particular emphasis on the detection system.

The next generation of Cosmic Microwave Background (CMB) instruments is dedicated to the detection of CMB B-modes. Instruments like QUBIC (QU Bolometric Interferometer for Cosmology) need components with state of the art properties at high frequency (>90 GHz) to minimise instrumental systematic effects. The Orthogonal Mode Transducer (OMT) is a critical front end component as it allows the discrimination of the polarisation mode of light. Superconducting planar technology seems very promising to improve its properties and miniaturisation. We present a planar superconducting OMT operating in the W band (75–110 GHz). Design and simulations have been performed using CST Studio Suite. Laboratory characterisations were obtained with two different cryogenic setups. We will present these two cryogenic setups, the calibration procedure and preliminary results for two OMT samples.

New techniques in microelectronics allow to build large arrays of bolometers filling the focal plane of submillimeter and millimeter telescopes. The expected sensitivity increase is the key for the next generation of space experiments in this wavelength range. Superconducting bolometers offer currently the best prospects in terms of sensitivity and multiplexed readout. We present here the developments led in France based on NbSi alloy thermometers. The manufacturing process of a 23 pixel array and the test setup are described.

The Q&U Bolometric Interferometer for Cosmology (QL’BIC) is the first bolometric interferometer designed to measure the primordial B -mode polarization of the Cosmic Microwave Background (CMB). Bolometric interferometry is a novel technique that combines the sensitivity of bolometric detectors with the control of systematic effects that is typical of interferometry, both key features in the quest for the faint signal of the primordial B -modes. A unique feature is the so-called “spectral imaging”, i.e., the ability to recover the sky signal in several sub-bands within the physical band during data analysis. This feature provides an in-band spectral resolution of ∆ v / v ~ 0.04 that is unattainable by a traditional imager. This is a key tool for controlling the Galactic foregrounds contamination. In this paper, we describe the principles of bolometric interferometry, the current status of the QU BIC experiment and future prospects.

NIKA (New IRAM KID Arrays) is a dual-band imaging instrument installed at the IRAM (Institut de RadioAstronomie Millimetrique) 30-meter telescope at Pico Veleta (Spain). Two distinct Kinetic Inductance Detectors (KID) focal planes allow the camera to simultaneous image a field-of-view of about 2 arc-min in the bands 125 to 175 GHz (150 GHz) and 200 to 280 GHz (240 GHz). The sensitivity and stability achieved during the last commissioning Run in June 2013 allows opening the instrument to general observers. We report here the latest results, in particular in terms of sensitivity, now comparable to the state-of-the-art Transition Edge Sensors (TES) bolometers, relative and absolute photometry. We describe briefly the next generation NIKA-2 instrument, selected by IRAM to occupy, from 2015, the continuum imager/polarimeter slot at the 30-m telescope.