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.

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 purpose of this project is to create a new generation of integrated mechanical micro-resonators for high-selectivity and sensitivity gas photoacoustic detection (sub-ppm concentrations), in a very compact, robust, portable system. In photoacoustic spectroscopy, measurement is performed by a microphone or mechanical resonator, using the acoustic pressure generated by the local warming caused by optical absorption. Mechanical resonators installed in the gas chamber provide high sensitivities, but they are not specifically developed for this application. The NOMADE project aims to develop micro-resonators specially designed for this application. A significant gain on the detection performances is expected. This new technology will allow placing the laser next to the micro-resonator, eliminating the need for any optical element. This compactness allows totally rethinking gas sensors, which can now be understood as a modular element easy to integrate in a more complex system.

Photonic Force Microscopy (PFM) is a scanning probe imaging technique based on optical tweezers. As in Atomic Force Microscopy (AFM), a probe raster scans the sample and provides details of its topography at the nanometer level. Instead of the rigid cantilever used in AFM, PFM employs the focused laser beam of optical tweezers to manipulate the probe. This has the potential advantage to apply a much lower force on the sample (a fraction of pN), and therefore to avoid artifacts and damages encountered when scanning soft materials like living cells. In our project, we aim to bring PFM closer to applications. Using specific nanofabricated probes, we will increase the resolution of the technique, and proposing both technical ameliorations and completely novel modalities, we aim to make PMF a mature, versatile, and wide spread technique.

High Operating Temperature Ga-free superlattice photodetector and focal plane array for the full MidWave InfraRed spectral domain (HOT-MWIR). An Increase of the operating temperature of the high performance cooled infrared (IR) detector focal plane arrays (FPAs) would induce a reduction in size, weight and power consumption of the cryocooler and allow a new class of applications where the needs in portability, compactness and energy autonomy of the IR cameras are essential. Currently, the photodetector technologies operating at high temperature (T= 150K), in particular the detector based on InAsSb, only cover a part of the midwave infrared (MWIR) domain, below 4.2µm. The extension of the cutoff wavelength to the full MWIR spectrum until 5µm for an operating temperature equal to 150K or higher, with no tradeoffs in performance, would present evident radiometric advantages. Combining the advantages of superlattice (SL) nanostructures in term of tuning of cut-off wavelength and the ones of XBn barrier structure device, the main objective of the HOT-MWIR project is to fabricate and study the first Ga-free InAs/InAsSb type-II superlattice (T2SL) photodetector FPA. The Ga-free T2SL photodetector on GaSb substrate will be designed in an XBn configuration with a 5 µm cutoff wavelength in order to address the full MWIR domain. Ga-free SL detectors and 320x256 FPAs (TV/4 format), with a 30 µm pixel pitch, will be processed, hybridized and evaluated for temperature operation over 150K. To reach this challenging objective, the HOT-MWIR project involves five French laboratories with complementary scientific and technological skills : three academic labs (IES, LPA, ILV), one industrial partner (THALES - III-V Lab) and an EPIC (ONERA - public undertaking). These multidisciplinary skills are required to investigate fundamental and applied researches, from the MBE growth of InAs/InAsSb SL structures to the hybridization on read out integrated circuit (ROIC) and to the radiometric characterizations of the FPA, together with detailed studies on optical properties of nanostructures, device physics and chemistry of surfaces and interfaces, using accurate k.p. modeling and magneto-spectroscopy performed on antimonide-based (Sb-based) SL nanostructures, etching and surface passivation of single device and arrays as well as the removing of the GaSb substrate using environmental and safer process ("REACH" conditions). Considering the many challenges addressed within the project, 48 months are planned to achieve and assess the first MWIR Ga-free T2SL FPA prototype.