This project intends to design, fabricate and study advanced III-V semiconductor nanostructures-based devices for the generation of coherent optical frequency combs (OFCs) with controllable transverse patterns dynamics. Our approach consists in an optically-injected vertical-emission Kerr Gires-Tournois Interferometer (KGTI) integrated in a compact free-space cavity. The KGTI shall consist in a (Al)GaAs/InGaAs metasurface-based VCSEL, with controlled light confinement and phase dispersion, to enhance fast nonlinear light-matter interaction. The coupled-cavity system will be designed to reach the bistable regime and achieve coherent light states with properties overcoming current limitations for telecom and imaging applications. This new experimental framework will be complemented by the development and bifurcation analysis of a hybrid time-delayed, partial differential equations 3D theoretical model, that includes both transverse 2D diffraction and on-axis temporal dynamics. The external cavity design will allow to pass from a single transverse mode to a highly transverse degenerate (self-imaging) system. In that latter case, we envision the possibility to generate multiple, spatially independent, OFCs. We expect this project to yield as a final product, a first experimental demonstrator of vertically-emitted 1D and 3D OFCs in a mature planar III-V semiconductor based platform. Our vertical KGTI will allow to produce combs with high coherence, low power consumption, GHz repetition rates, and containing hundreds of lines in the near infrared spectral domain, with, thanks to the planar vertical architecture, potentially 10 × 10 transversally multiplexed and reconfigurable beams.These results will have groundbreaking applications for instance in massively parallel comb generation or for double comb sensing application and it will help to overcome several limitations for telecom applications. On the technological and experimental sides, the technical barriers to be lifted consists in developing a microcavity containing a nonlinear material having a very high value of the Kerr nonlinear coefficient. For this objective we plan on using the almost untapped potential of AlGaAs-based semiconductor materials operated below their band-gap. The nonlinear interaction will benefit from the strong light confinement in the microcavity. The microcavity design shall find a compromise between the width of the frequency comb targeted as well as the value of the optical power one wishes to inject into the KGTI system. Critical power threshold for the formation of Kerr combs can be controlled via the external cavity reflectivity and imaging configuration, and detuning of the optical pumping with respect to the microcavity resonance; the sign of the latter allowing also to explore both anomalous and normal dispersion regimes. On the theoretical side, the modeling of the system we wish to realize necessitates using Delay Algebraic Equations (DAEs). While the latter have a great potential for the modeling of dispersive phenomena in photonic systems, their studies is comparatively less developed than those of partial differential equations (PDEs). In addition, if DAEs are the natural choice for studying temporal dispersive dynamics, the diffractive propagation of light in the transverse plane of the cavity as well as field curvature effects induced by lenses and mirrors require using PDEs. As such, a full 3D model shall consists of a hybrid DAE-PDE system whose analysis is way beyond the state of the art and represents an exciting and challenging endeavor. The theoretical aspects of KOGIT will also significantly advance the study of spatio-temporal phenomena in nonlinear media. The proposed experimental framework will be complemented by the development of bifurcation analysis method of a hybrid DAE-PDE system that will constitute a qualitative jump in the state of the art.

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.

This project aims at developping nanostructured spectral filters made of semiconductors, contrary to usual materials (metal and dielectrics). We will address the LWIR spectral range. We follow two goals: - we will demonstrate monolithic integration of the filters on T2SL photodetectors - we will demonstrate the ability to realize dynamic spectral filtering thanks to electrical actuation. The target is the scan of several hundreds-wide spectral range, with a maximum voltage of 5V. To reach these goals, we will rely on semiconductors such as GaSb and heavily doped InAs (HDS - heavily doped semiconductor). Thanks to heavy doping, InAs will have "metallic" properties in the spectral range of interest. This HDS can be thus used instead of metals in usual nanostructured filters architectures. Furthermore, T2SL photodetectors are also made of InAs, GaSb and other material with the same lattice parameter. Thus, the monolitic integration of the filter on the photodetectors is possible. Then, we will study a mechanism of tunability based on the move of the free carriers in the HDS, when voltage is applied to the component. The concentration of these carriers will then be higher in the vicinity of a barrier, and refractive index will there be modified. If the barrier is properly placed in the nanostructured component, the resonant conditions will lead to a modification of filtering wavelength. Four components will be fabricated and each of them will be designed, fabricated and characterized. These components are: - nanostructured spectral filter made of semiconductors : this will validate the conception experimentaly - a LWIR photodiode with a nanostructured spectral filter on it : this will validate the monolitic integration - a component without nanostructures which will allow to validate experimentaly the barrier - a tunable nanostructured spectral filter grown on photodetector, which is the final goal of the project The work will be divided into three parts: - conception (electromagnetism to design nanostructures and electronics to design the barrier) - nanofabrication of components in clean-room - characterisation (experimental validation of the optical functions) We believe that these components will be building blocks for the next generation of multispectral imaging system with high frequency acquisition. These building blocks will break the traditionnal compromise between spatial and spectral resolution. Besides, the concept of tunability with barrier could be used in other applications, such as nanostructured thermal sources. Two laboratories will be part of the consortium : (1) ONERA, leader, where conception of nanostructures will be done and also electro-optical characterization of components ; (2) Montpellier University, where epitaxial growth, most of fabrication process and conception of barrier will be done. We underline the fact that promising experimental and theoretical results have been obtained by our teams these last months. These results have not been published yet, but a summary is described in the proposal.

Information technology requires more and more high-performing devices for information encoding and processing. In this regard the use of optical solitons as information bits appears promising, especially if implemented in fast, compact and cheap devices as semiconductor lasers. In particular, "light-bullets" (LB), where the light would be localized in the three dimensions of space, are expected to lead to disruptive performances in terms of bit rate, resilience and agility. The aim of this project is to conceive, to realize and to operate semiconductor laser devices for the generation and control of spatiotemporal solitons, also called “light bullets” (LB). LB will be implemented in Vertical External-Cavity Surface Emitting semiconductor devices mounted in an external cavity configuration (VECSEL) closed by a saturable absorber mirror (SESAM). Devices fabrication will be developed in the frame of this project to match the parameters requirements for LB existence. Once LS will be obtained and characterized, their application to information processing will be addressed by targeting a three-dimensional all-optical buffer. LB have been chased in conservative systems since the pioneer work by Silberberg at the beginning of ’90. The propagation of an optical pulse in a medium where diffraction and anomalous group dispersion are both compensated by a non-linearity is strongly unstable and, despite the efforts made, it is impossible to avoid the pulse to collapse or to spread. The originality of our approach to LB consists in implementing them in dissipative system, where LB will appear as stable solutions for a wide set of initial conditions and control parameters. In addition, when the system is strongly dissipative, LB can be individually addressed by an external (optical) perturbation and used as information bits. More precisely, LB we are aiming at in this project are spatio-temporal “Localized Structures” (LS). LS have been observed in the transverse section (spatial LS) and in the longitudinal direction (temporal LS) of optical resonators. Several experiments have disclosed the potential of LS for information processing, especially when implemented in fast and scalable media as semiconductor resonators. LB we will obtain will lead to three-dimensional buffering of data inside the VECSEL external cavity. If the transverse section of the device allows creating an array of NXN spatial bits and the longitudinal cavity allows for storing M bits, one may handle MXNXN bits in a single device by using LB as information bits. The temporal bit rate is accordingly increased by a factor given by NXN with respect to single-transverse mode resonators. The performances obtained in past experiments in semiconductor lasers lead to an estimation of 5 Kbit sequences stored in the cavity and a writing/reading bit rate of 100 GS/s. Beyond information processing, LB are very interesting for other applications where picoseconds laser pulses are required at an arbitrary low repetition rate and at an arbitrary pattern sequence (time-resolved spectroscopy, optical code division multiple access communication networks and LIDAR). The possibility of integrating metasurfaces onto the VECSEL or onto the SESAM will induce vorticity to each light bullet, thus enabling the creation of an array of optical tweezers for parallel manipulation of biological nano-objects. The use of semiconductor lasers for supporting LB is an important aspect of our project. If implementation of LB in semiconductor lasers enhances their attractiveness for applications, the conception and manufacturing of devices able to sustain these structures is challenging and a large part of the project will be devoted to devices optimisation.

The IES Lab UMR 5214 (University of Montpellier) which has sensor's skills on flexible substrates and the company TAGEOS SAS specialized in the production of RFID (radio-frequency identification frequency identification) low cost paper, wish to establish a joint laboratory for the commercialization of RFID tags with sensor and to meet market requirements. Both partners know and share a strong commitment to innovation through this joint laboratory. Labels must be produced in large volumes while respecting the environment and a relatively minimal cost. The target markets are those of "smart packaging" food and pharmaceuticals but also medical device (POC).