The rise of a vast family of two-dimensional (2D) crystals, with unique electronic and optical properties, has opened exciting perspectives for “van der Waals heterostructures”. The latter are only a few atoms thick and exhibit new properties and functionalities that cannot be achieved using bulk crystals. Indeed, 2D crystals feature exposed electron gases, which properties are dramatically influenced by non-covalent coupling to low-dimensional adsorbates. So far, most endeavors have focused on heterostructures based on graphene, boron nitride, and transition metal dichalcogenides (MX2, with M=Mo, W and X= S, Se, Te). In particular, graphene, as a 2D semimetal with extremely high carrier mobility but no bandgap and “monolayer” MX2, as direct bandgap semiconductors with good carrier mobility, are highly promising building blocks for optoelectronic devices (OEDs). Besides, 2D crystals are naturally suited for lateral geometries and can be more easily integrated in OEDs than 0D and 1D nanostructures. Yet, the fabrication of high-quality heterostructures based on graphene and MX2 relies on sophisticated processes, which offer limited scalability and device engineering possibilities. At the same time, a breakthrough has been achieved in the controlled colloidal synthesis of layered semiconductors, such as core only, core-shell and core-crown 2D nanoplatelets (NPL, or quantum wells) based on metal chalcogenides (CdSe, CdS, CdTe,…). NPL are excellent light-absorbers and emitters. Their thickness, which directly defines their electronic structure and peak emission energy, is controlled at the monolayer level, while their lateral dimensions can attain the µm range. In addition, NPL surface chemistry can be efficiently tailored. Importantly, highly homogeneous ensembles of NPL, with high structural quality can be synthesized, processed and integrated into OEDs. Nevertheless, electron transport in NPL films remains driven by hopping processes, leading to limited carrier mobility. It therefore seems natural to combine i) graphene and MX2, as semimetallic or semiconducting channels with good transport properties and ii) NPL, as a tunable active materials, into novel hybrid 2-dimensionnal heterostructures (H2DH) and OEDs. The performance of such devices is governed and often limited by band alignment, interactions with the underlying substrate, and crucially, short range phenomena such as charge separation, charge transfer and Förster resonant energy transfer (FRET). FRET is a “dipole-dipole”, non-radiative coupling phenomenon, involving a photoexcited donor and an acceptor, which absorption spectrum overlaps with the emission spectrum of the donor. FRET between a photoexcited NP and a graphene or MX2 layer may bypass direct charge transfer processes, which could lead to an electrical current, useful for optoelectronic applications. FRET may be seen as an efficient way to harvest and funnel energy from photoexcited donors, which is of major interest for photodetection. However, in the absence of a charge separation mechanism, the energy transferred as electronic excitations will be rapidly dissipated into heat. H2DH offer a natural and elegant platform to address these issues and to uncover new regimes of electron transport, charge separation, photoconductivity, photodetection and electrically-controlled luminescence. For our project, we will grow high quality 2D materials (graphene, MX2, and NPL) that will be assembled intro electrically contacted H2DH, using original fabrication methods based on resist-free processing and electrochemical gating. We will investigate the fundamentals of charge and energy transfer in NPL-graphene and NPL-MX2 H2DH using a complementary set of optical and electron spectroscopy studies, as well as optoelectronic measurements. This fundamental work will guide a more applied, yet equally important effort towards the development and extensive study of a new class of phototransistors based on H2DH.

In this project, we will develop a new type of hybrid metal/semiconductor laser source exploiting the strong potential of optical Tamm modes. These modes, which have recently been highlighted in the optical domain, exist at the interface between a metal layer and a dielectric Bragg mirror. In our case, The Bragg mirror is containing quantum wells. These modes present many features that can be advantageously exploited both for the realization of photonic or plasmonic sources. Indeed, due to their hybrid metal/dielectric nature and to their particular dispersion relation, they should enable a coupling either to the optical modes in the light cone or directly to the plasmon mode. They also present much lower losses than conventional plasmons modes and can be controlled and laterally confined by a simple patterning of the metal layer. Finally, the metallic layer opens the way to the electrical injection of the structures for the realization of photonic or plasmonic integrated sources. From a fundamental point of view, this study is part of a general trend in plasmonics which aims to cut losses while maintaining key properties of plasmons (spatial localization, spontaneous emission enhancement, lasing). Three goals will be pursued in parallel: • The first goal is the demonstration of an electrically injected and laterally confined laser source. We will first focus on the demonstration and optimization of lasing under optical pumping in Tamm structures confined by a metallic disk. The amelioration of the optical properties of the structures associated to the confinement (quality factor, enhanced beta factor, reduction of laser threshold) will be studied experimentally but also by theoretical modeling. The design of the structures for the electrical injection will be developed in parallel. In a second step, the degree of freedom opened by the easy structuration of metals will be used to design refined geometries in order to control the polarization of the emitted light or to exploit gallery modes present in these structures. • The second goal is to form a bandgap in the Tamm dispersion relation by a periodic nano-structuration of the metallic layer only. Photonic crystal cavities will be realized in order to increase the field confinement without additional losses, control the emission direction and reduce the device size. This approach relies on a well mastered technology and induces no degradation of the active layer during the process since only the metal is patterned. Periodic Tamm structures will be modeled and characterized in order to evaluate the impact of the patterning on the emission properties of the structures, and optimize lasing in terms of threshold and emission directivity. • The third goal is to exploit the hybrid metal/dielectric nature of the Tamm modes as well as their compatibility with an electrical injection in order to develop surface plasmon sources. Two directions will be investigated: on the one hand a coupling between the Tamm and the plasmon mode via a grating on metal, and on the other hand a direct coupling between these two modes. Modeling and optical characterization will be implemented to identify and optimize the Tamm/plasmon coupling in both configurations, in order to finally exploit this coupling for the realization of plasmon sources. The realization of this project will not only lead to a better understanding of the physical effects associated with these new modes, but also pave the way both for the development of new types of laser structures whose properties could be controlled by simple technological processes, and to devices enabling the conversion of localized electrical excitation into surface plasmons.

Numerous chemical or biological processes involve the transport of macromolecules through tiny channels of nanometric size. We have been the firsts in France to study these processes (as early as 2003) using natural channels and artificial channels obtained by drilling nanopores in ultra-thin SiC and Si3N4 solid-state membranes with a Focused Ions Beam Apparatus (FIB). The molecules passing through a pore are detected by a simple electrical method. We would like to pursue this research by developing their different aspects : fabrication, detection and applications. We first propose to drill nanopores in single sheets of graphene by using an optimized system of focused Gallium or Helium ions beam, and then to study its use as an ultra-fast DNA and proteins sequencing tool. This domain, which we explore since two years is growing explosively. For what concerns detection, we wish to develop the optical and mechanical detection of the translocation of a macromolecule through a nanopore. The optical detection requires the use of fluorescent or luminescent macromolecules. Spurious light created while illuminating a pore is eliminated by absorting it or by hindering its propagation (condition of zero mode waveguide). This is obtained by coating the surface of the pore and of the silicon nitride membrane by silicon or gold.The mechanical detection of the forces exerted on a macromolecule confined in a nanopore is obtained when the molecule is attached to the tip of an atomic force microscope or to a bead trapped in optical tweezers. We propose to measure the work exerted on a translocating (out of equilibrium) macromolecule and to use the recent Jarzynski’s relation for studying the energetic lanscape explored by the molecule. Our experience in drilling nanopores by focused ions beam enables us to make nanopores in various materials, controlling their size, their position, their organization We are also able to produce a large amount of nanopore which may serve the needs of research laboratories and future applications. We have constructed our project in order to propose valuable applications of nanopores in the fields of Biology and Biotechnoly, avoiding the well-know application to DNA sequencing, which is outside our scope. We have made a association with a small spin-off company created by a partner laboratory of this consortium in order to study the production of DNA vectors for gene tranfer and gene therapy by molecular extrusion through a nanopore. An electric field or a pressure force the passage of a DNA plasmid through a Silicon Nitride Nanopore and put the molecule in contact with a solution of cationic polyelectrolyte at the exit of the pore. An electrostatic complex is formed with a controlled size and composition, with a single DNA molecule per nanoparticle. We propose to use the same principle of molecular extrusion for studying the synthesis of polymers through a nanopore coated with a suitable catalyst and for controlling the folding and unfolding of proteins buy nanopores. We will use a new experimental prtein model, the Luciferase protein, which allows an optical detection of its transport and functionnal foldind after translocation through a nanopore. We thus hope to create new biomimetic objects enabling the analysis and manipulation of macromolecules with a never achieved spatial and temporal resolution

Digital and analytical functions performed by today’s semiconductor devices are governed by the electronic transport across an engineered material system with a well-defined electronic structure. Even if a multitude of electrons are concerned in the device operation, the device fundamental characteristics arise from properties inherent to single electrons. For instance, photon emission is related to transitions between electronic states of the system and for optoelectronic devices operating in the mid and far infrared wavelength range is characterized by an extremely long spontaneous emission time (>100ns), which hinders the realization of efficient light emitting diodes. In this project we plan to realize novel optoelectronic devices, whose performances do not belong to single electron properties, but rather depend on the ensemble of the interacting carriers. We recently demonstrated that the optical properties of a dense electron gas do not reflect the energy spectrum, but depend on the Coulomb interaction between electrons. The absorption spectrum of a semiconductor quantum well with several occupied energy levels presents a single absorption peak at an energy completely different from the single particle transition energies. This unique optical resonance, concentrating the whole interaction with light, corresponds to a many-body excitation of the system, the “multisubband plasmon”, in which the dipole-dipole Coulomb interaction locks in phase the optically allowed transitions between confined states. In this project, the peculiar properties of multi-subband plasmons will be exploited for mid and far infrared optoelectronics. The first property is the fact that, as the permittivity of multisubband plasmons depends on the doping level and on the size of the quantum well, semiconductor layers with ad hoc dielectric properties (hence metamaterials) can be realized. As a first application we will design all-dielectric waveguides in the mid and far infrared for quantum cascade lasers. A second application will be the design of engineered infrared absorbers. The second part of the project is based on another fundamental property of collective electronic excitations: their superradiant nature. Indeed the multisubband plasmon is the bright state issued from the coherent superposition of several intersubband excitations. As a superradiant state can be visualized as one in which a macroscopic polarization is established over a region of space, a very interesting way to characterize this state will be its observation by using Electron Energy Loss Spectroscopy. The superradiant nature of multisubband plasmons results in a radiative lifetime of the order of few hundreds fs, thus much shorter than the typical intersubband spontaneous emission lifetime. We will exploit this property to conceive and realize two different classes of optoelectronic infrared emitters based on many-body excitations: - Quasi-monochromatic fast and tunable incandescent sources - Quantum engineered superradiant emitters The first kind of devices is based on the same geometry as a field effect transistor: the electron gas is excited by a source – drain current, while the electronic density can be controlled by a gate voltage. This point will be also studied in collaboration with STMicroelectronics, which will provide FDSOI and CMOS devices, in order to observe far-infrared optical signals in state-of-the-art electronic devices. In order to fully take advantage of the superradiant character of multisubband plasmons, another generation of devices will also be conceived, realized and characterized, using quantum engineering for resonant excitation. We will design a device based on vertical transport through the electron gas, a plasmon assisted tunnelling device. More selective injection mechanisms will also be investigated, by exploiting the dipole-dipole interaction in systems of tunnel coupled quantum wells.

The goal of the project is to study the potential of optical semiconductor microcavities as THz detectors and emitters. We propose here to explore the possibility of detecting and generating THz radiation in semiconductor microcavities by using THz radiative transitions between polaritonic states. Polariton physics is now well known and especially well mastered by the three project partners (LKB, LPA, LPN). The investigated polariton states are separated in energy by typically a few meV (i.e. in the THz range). If the THz radiative transitions between the polariton branches are normally forbidden by the selection rules, different theoretical proposals open the way for engineering the band structure to allow the absorption or radiative emission of THz photons. A particularly interesting aspect of this project lies in using the peculiar properties of polaritons to avoid the low temperature constraint usually required by thermodynamics principles. The objective of the project is the realization of THz detectors operating at liquid nitrogen temperature with high detectivity in compact geometries, compatible with the development of semiconductor based devices. Conversely and in similar schemes, we will study the potential of such semiconductor microcavities for THz emission by using the bosonic stimulation regime (polariton lasing).. Different strategies proposed by the theory to allow THz radiative transitions will be implemented in the design and fabrication of a new family of semiconductor microcavities and micropillars. These structures will then be studied in the field of optics and THz using methods controlled by three partners: - LPA brings its expertise and experimental facilities in the field of THz spectroscopy, optical spectroscopy and theory - LKB brings its expertise and experimental facilities in the optical study of polaritons under "two-photon" and non-linear excitation of the polariton states - LPN provides expertise on the sample fabrication as well as its expertise on polariton lasers.