TeraHertz (THz) radiation is of importance for both fundamental science and for technology with promising applications in astronomy, chemistry, bio-security and communications. However, the THz frequency range (especially from 1 to 10 THz) remains one of the least technologically developed spectral regions owing to the lack of compact powerful sources. The STEM2D project tackles the challenge to achieve an integrated powerful THz–submillimeter wave emitter based on 2D materials operating at room temperature. The novelty here will be to exploit synchrotron-like radiation process in corrugated 2D materials. Synchrotron-like radiation process is well established in the context of vacuum electron-beam devices such as free-electron lasers but represents an original concept for light emission in condensed matter. Moreover, the use of geometrical constraints (corrugation) as opposed to the application of an external magnetic field (such as in wigglers) to obtain radiation via angular motion is innovative. 2D materials (such as graphene) are very attractive for this concept. Indeed, due to their ultra-small thickness (i.e., single-atomic-layer), the conformal adhesion of 2D materials to a corrugated surface can be expected with sub-micron grating periodicities. More specifically, in graphene, the carrier velocity is about an order of magnitude larger than the maximum drift velocities achievable in typical semiconductors so the output THz power is expected to be high. In addition, the other 2D materials, such as MoS2 and black phosphorus (BP), even if the carrier motilities are lower, possess a band gap providing a large control of the carrier-density using a gate electrode. So, synchrotron-like emitters based on these 2D materials could emit THz light modulated at GHz frequency with a high contrast that is particularly attractive for communication applications. Combining cutting-edge nanofabrication techniques, advanced THz experiments and sophisticated microscopic modeling, we will investigate fundamentally interesting and technologically promising corrugated 2D materials radiation devices. Therefore, this proposal relies on three major objectives: i) the theoretical study of corrugated 2D materials and of their coupling with optical cavity, ii) the demonstration of fully integrated THz emitters based on corrugated graphene and iii) the extension of this concept to other 2D materials to efficiently modulate the THz emitted radiation at high frequencies using a gate. To achieve these objectives, several challenges will have to be tackled. The main technological challenge is to achieve high quality corrugated substrates and efficiently transfer the 2D materials onto them. The instrumental challenge is to detect the weak THz radiation that will be emitted by the first series of devices (not yet optimized). The main scientific challenge is to theoretically investigate the coupling of corrugated 2D materials to an optical cavity. Indeed, innovative approach has to be proposed to synchronize the THz radiation emitted by the device (of micrometer dimensions) to the run-trip time of the THz waves propagating in the optical cavity (of few hundreds micron length). The global impact of STEM2D will be considerable by pointing the route for a new concept exploiting corrugated 2D materials and demonstrating its pertinence in THz technology. The project STEM2D will be carried out by 1 industrial partner Thales Research and Technology (TRT), 3 academic partners as (a) Institut d’Electronique et des Systèmes (IES) from Montpellier University, (b) Laboratoire de Physique de l’ENS (LPENS) and (c) Unité Mixte de Physique CNRS/Thales (UMPhy).

The SuperQIF project aims at initiating the development of a low-field MRI system which is intended to be inexpensive, open-spaced for both patients and physicians, and more equitably spread across the territory. To do so, it is proposed to transfer a new class of ultra-sensitive detectors in low-field Magnetic Resonance Imaging. This very high sensitivity allows to compensate for the lack of signal usually undergone at low fields, hence the use of open MRI systems which are more comfortable for the patients, cost-effective and as efficient as conventional high-field systems. There is a big potential outcome of this technological breakthrough on public heath and industrial renewing.

The detection of chemical compounds present at ultra-trace levels is a major concern for our societies and applies to a very wide range of applications: protection of citizens against terrorist threats, safety of workers exposed to dangerous substances, monitoring of the environment quality … Among the different existing chemosensory devices those based on the fluorescence are the most sensitive. To further amplify this inherently sensitive method, increasing emphasis in analytical science has been directed towards the development of new materials such as: conjugated polymers. However substantial improvements in the sensitivity of chemical sensors are still necessary to reach the performances required for ultra-trace detections. In this context, the project ambitions are to propose a global approach including innovative technological solutions to improve chemosensors sensitivity and response time. The aim is to demonstrate that the performances of those sensors can be drastically improved (orders of magnitude increase) by controlling the fluorescent materials emission using engineered substrates. Recently, it was reported that the sensitivity of semiconducting luminescent polymers used for TNT detection could be increase by a factor of 30 working near the stimulated emission threshold. In this project, we propose to use optically active nanostructured (ZnO) substrates to further improve the detection threshold of fluorescent polymers based sensors. Fluorescent properties of the sensitive polymer will be combined with the self organisation, refractive and luminescent properties of ZnO nanostructures leading to hybrid device with optimized active surface, luminescent efficiency and lasing threshold.

Since the first demonstration in 2002-2003, of the solid-state quantum cascade laser (QCL) operating at terahertz frequencies (THz, typically spanning from 500 GHz to 5000 GHz), there has been a great renewal of interest for this part of the spectrum, especially for security, non-destructive testing, environmental, pharmaceutical and medical applications. For security indeed, ambitious projects have been supported to date which, from a scientific and technical point of view, provided excellent results. Unfortunately the demonstrations were obtained with a too moderate applicability: although overall systems have proven unique potential in this field, they remained complex, bulky and mostly unable to demonstrate real time operation, especially for remote detection. Furthermore, one can believe that the lack of really operational systems mainly results from too limited efforts towards the realisation of compact and high performance THz sensing module chains. At the same time, heterodyne THz detectors/mixers based on superconducting hot electron bolometers (HEB) have been optimized for radio-astronomy, to reach ultimate sensitivity close to a few THz photons per second, but with the drawback of cryogenic cooling down to 4 K. The alternative solution for high sensitivity heterodyne detection at 300 K is to use Schottky diodes. In this case limitations come from the power level required of the local oscillator (LO), increasing with frequency up to some mW at 2 THz (compared to a few tens of nW with a HEB). So it becomes difficult to address all the frequency range of interest for security applications. In between 4 K and 300 K, high critical temperature superconducting (HTS) materials, operating around 77 K, have reached a high level of maturity that permits implementation of high performance microwave devices. Moreover, these devices can be implemented in very compact closed circuit cryogenic coolers (about 400 cm3). According to these considerations we believe that: (i) a highly sensitive, compact and easy-to-use THz detector is the missing building block which could warrant, beyond the implementation of THz remote sensing systems, the advent of really applicable THz systems; (ii) such a compact and high performance THz (coherent) detector could result from the combination of the existing knowledge on HEB mixer design with the high quality of nowadays HTS materials; (iii) compactness and usability of the final THz coherent detector will benefit from the compactness of closed circuit cryocoolers around 70 K in which it will be possible to implement a HTS HEB mixer, and a THz QCL LO source, as well. In this applicability context of very compact coherent detection systems to the potentially wealthy market of THz detection, MASTHER aims at implementing a heterodyne receiver made from a sensitive lightweight cooled (80 K) HEB mixer chip with its solid state THz QCL source (at 60 K) as local oscillator in miniaturized cryocoolers. MASTHER will be therefore a portable THz detection system with good sensitivity and reduced cost. The partners of the proposed consortium are: LGEP (SUPELEC-CNRS-Univ. UPMC Paris 6 and Paris Sud 11), coordinator, with CEA-INAC (sub-contractor); UMPhy (Thales-CNRS); MPQ (Univ. Paris Diderot-CNRS) and Thales Research & Technology. The MASTHER project comprises 5 tasks: 1) Coordination (LGEP), 2) HTS (YBaCuO material) growth and HEB physics (LGEP/CEA & UMPhy), 3) Realization of YBaCuO HEB mixers and laboratory tests (LGEP), 4) Realization of QCL THz sources and tests (MPQ), 5) Integration and MASTHER prototype demonstration (TRT). In practice, it will combine expertise of the 4 partners, which will closely interact with each other during the whole duration of this industrial project. At the end, a miniaturized all solid state 2.5 THz receiver should be integrated and available for test to exhibit the capability of detecting an object of 10 to 20 degrees differential temperature range at a few metres distance.

Numerous detection applications rely on the optical properties of atmospheric transparency windows around 1.6 and 2.3 µm. Thanks to advances in laser source technology, a large range of illumination techniques is now available to actively probe various scenes and objects, sometimes very far from the observer (applications to telemetry or identification by long range imaging) or screened by partially absorbing or diffusing media on the optical path (applications to biology and remote spectroscopy). Yet, the corresponding optical signal analysis generally suffers from the sensitivity of infrared detection devices. Following promising preliminary results recently obtained by the two partners, Thales Research & Technology (TRT) and the laboratoire Kastler-Brossel (LKB), the COSMIC project revisits the idea of frequency converting the multimode infrared signals of interest to shorter wavelengths by sum frequency generation with a secondary pump source. This makes infrared detection around 1.5 or 2.5 µm possible with all the technological and economic advantages of silicon based detectors. COSMIC stakes thus cover two aspects. Concerning modelling tools (derived from quantum metrology and applied to the specific case of imaging with classical noise), we need a trustworthy evaluation of the potential of multimode approaches for sum frequency detection, either to simulate active imaging systems (conversion efficiency, influence of pump laser design) or to study fundamental limits (parameter estimation by modal decomposition with applications to the separation of close incoherent sources and to detection at low light levels or through diffusing media). Experimentally, the partners also intend to exploit and secure their advance compared to competing European teams, following two complementary tracks. In the first part of the project, LKB will implement a modal sorter without frequency conversion and TRT will build an active imager around 2 µm based on multimode sum frequency generation on a CMOS camera and suited to the study of outdoor scenes at short range, resolved or not. The key point that will guide its design is the possibility to use the same pulsed fiber laser for both illumination and pumping of the frequency conversion stage. This advantage will be decisive to ensure a successful insertion in future systems. Those experiments will be merged in the second part of the project to study the mutual benefits of multimode frequency conversion and spatial mode selection in the case of weak and complex infrared signals at the core of COSMIC motivations. Those theoretical and experimental developments will be evaluated during the project with a constant goal of valorization toward detection applications. The partners have already identified a network of academic and industrial contacts able to feed the project with reliable specifications of practical cases, leading to an efficient selection of maturation paths for the COSMIC concept.