Fast amplitude and phase modulation is essential for a plethora of applications in photonics, including laser amplitude/frequency stabilisation, coherent detection, optical communications, spectroscopy, gas sensing etc. In the mid-infrared (MIR) wavelength range (3-12um) broadband MDs are missing, hampering the progress of MIR photonics. In this project we aim at demonstrating two types of power efficient and broadband (up to ~40GHz bandwidth) integrated MIR amplitude- and phase-MDs, suitable for industrial production, that will be capable of addressing the needs of emerging MIR photonics applications. The frequency response of these devices (optimised in the 9.5-10.5um wavelength range) will be fully characterised using an in-house fabricated ultra-broadband (>70GHz) detector and a VNA analyser. Finally, the potential of the MDs for spectroscopy/gas sensing applications will be demonstrated by setting up an original high resolution-spectroscopy experiment.

This project aims at designing network of semiconductor nanolasers on silicon-on-insulator waveguide circuitry for neuromorphic computing applications. To design networks with many nano-lasers, the consortium will first play a special attention on designing energy efficient self-pulsating. These lasers will subsequently interconnected via the underlying silicon circuitry for neuromorphic computing applications. In this scheme, integrated Mach-Zehnder modulators will be used in order to allow to reconfigure the networks for different applications of neuromorphic computing.

One of the most promising features of topological matter is the presence of helical ballistic edge states, pure one-dimensional propagating electronic states protected from backscattering by spin-momentum locking. When coupled to superconducting electrodes, a supercurrent is carried by topological Andreev bound states (ABS) also presenting spin-momentum locking. However, we are still far from a complete understanding of the role of the spin degree of freedom and the parity conservation. A major issue is to find unambiguous experimental signatures of the topological protection. We propose to tackle this problem through measurements of the dynamics and relaxation mechanisms of such states, which is still poorly explored experimentally. Our general idea is to develop an ultrasensitive magnetic field sensor by combining cryogenic amplifiers adapted to giant magneto-resistive (GMR) sensors, both homemade. We plan to detect fluctuations of the supercurrent at equilibrium in topological material coupled to superconducting electrodes. These current fluctuations originate from thermal excitation of ABS on a time scale given by the inelastic relaxation time, which can be as large as few milliseconds. This makes possible the real time detection of supercurrent fluctuations. We thus propose to improve the bandwidth and sensitivity of GMR detector up to the MHz range in order to detect real time fluctuations of occupation of the topological ABS. We will use different topological materials (Bi nanowires, WTe2 and Bi4Br4) whose fabrication we master and on which we have evidenced edge states. Eventually, such a high sensitivity should allow us to detect persistent current created by 1D loops of helical edge states in topological systems without superconducting contacts. This would represent one of the most relevant and direct evidence of the topological states.

Record efficiency solar cells are made of III-V materials, but their usage is limited to niche applications due to their high cost. More than 80% of this one is made up by costly substrates, so that a method to recycle them for several consecutive growths would constitute a breakthrough for high-efficiency low-cost devices. As an appealing solution to answer this technological problem, this project aims at developing the remote epitaxy. It consists in the epitaxy on a crystalline substrate covered by a monolayer of graphene and was shown to allow the growth of transferable epilayers. While providing convincing results, the method raises fundamental questions regarding the particle interactions during growth. This project provides with a methodology to clarify those phenomena, as well as original developments for robust and controllable fabrication processes and ambitious objectives in terms of device performances. Beyond photovoltaics, this project also opens perspectives in fields such as silicon photonics or flexible opto-electronic devices.

RF signals are everywhere in today’s connected society. Surface Acoustic Wave (SAW) filters are widely used to distinguish between signals at different frequencies. Unfortunately, the performance of SAW filters drops above 5 GHz. Thin films of epitaxial LiNbO3 on sapphire host “guided” AW. These modes comply with the demand for higher frequency and higher efficiency. Unfortunately, despite the success of AW technology and its frequency progresses, two limitations remain inherent to AWs, specifically: (i) The absence of tunability once the geometry and material are defined. If several frequency bands are needed in an application, this requires several AW devices. (ii) The absence of non-reciprocity of acoustical wave propagation. In AW devices, the energy flows as easily in the forward and in the backward directions. The input of any AW device cannot be isolated from the influence of its output, as would be desirable for information processing purposes. Spin waves (SWs) are the eigenexcitations of the magnetization. They display rich linear and nonlinear physics and they offer the same miniaturization capability as acoustical waves. The dispersion relation of SWs can be engineered by material and geometry, and later adjusted finely by magnetic fields or spin-torque effects; Upon proper design, SWs can be strongly non-reciprocal, i.e. they propagate differently in opposite directions. The central hypothesis of our research is that coupling AWs with SWs is a route to overcome the intrinsic limitations plaguing acoustic wave technology: by researching at the interface between material science, magnetism, acoustics and microwave engineering, the objective of MAXSAW is to use specific features of spin-waves (SW) –tunability and non-reciprocity– to add new capabilities to state-of-the-art LiNbO3 AW-based filters. We will harness the ability to engineer the dispersion laws of both SW and guided AW to achieve tangential nesting of the propagation characteristics of AW and SW, i.e. match their frequency, wavevector, and group velocities. This last (novel) point, supplemented by the high confinement of the acoustical energy near the interface with the coupled spin-wave medium, ensures that even if the SW-AW coupling (i.e. the magneto-elasticity) is weak, truly magneto-elastic resonance with strong hybridized character can be harnessed and confer non-reciprocity and tunability to the wave propagating medium as well as to dedicated transducers. The end goal of MAXSAW is to demonstrate new rf components with unprecedented attributes: this includes adjustable delay lines, compact broadband isolators, and frequency-tunable filters all potentially perfectly adapted for 5G standards, that may offer valorization opportunities for us. To achieve its goals, MAXSAW comprises 4 technical work packages: WP1 defines the propagation medium for the hybrid waves by enhancing the magneto-elastic cooperativity. WP2 is devoted to the making of the propagation medium, including the acoustical materials growth and the customization of the magnetic materials. WP3 develops augmented transducers matched to the propagating medium to best benefit from the medium developments. Finally, the WP4 is the demonstration of novel rf devices that harness hybrid AW-SWs in the strong coupling regime. To demonstrate its objectives, the consortium shall build upon the expertise in state-of-the-art acoustic wave devices (FEMTO-ST, team of Pr. Bartasyte), spin-wave dynamics (C2N, team of Thibaut Devolder, coordinator), their mutual coupling (INSP, team of Laura Thevenard) and optimized non-reciprocal magnetic materials (CEA-SPEC, team of Grégoire de Loubens), complemented by the support of Frec|n|sys as industrial subcontractor.