The turbulent transport of flexible fibres is of paramount importance in a large range of industrial and environmental applications, from papermaking to sediment deposition in rivers and oceans. However, the dynamics of fibres in inhomogeneous and anisotropic turbulent flows, particularly relevant for these applications, has mainly been studied in numerical simulations and, only recently by a few experiments limited to rigid fibres. This project aims to go further in order to model the dynamics of long flexible fibres in wall-bounded turbulent flows. It relies on an experimental approach in a turbulent channel flow coupled with numerical simulations having similar control parameters. We will first study the rigid-flexible transition in the turbulent channel flow and compare it to the scaling law that has been obtained in homogeneous and isotropic turbulence. We will then study the effect of flexibility on the transport of the fibres in the turbulent channel flow, and particularly on their dynamics close to the walls. Finally, we will focus on the stretching of particles in wall-bounded turbulence, by investigating the coiled-stretched transition on home-made macroscopic polymers.

Multimode optical fibers are the subject of very active research in view of the technological advances expected in the fields of telecommunications and imaging. However, mode dispersion and coupling pose practical implementation problems. RICOTTA is a fundamental project inspired by this issue, which aims to study light scattering in multimode optical fibers with controlled disorder. Scatterers will be photo-inscribed into the fibers using a local direct laser writing device, and the coherent wave transport properties will be measured through the disordered fiber transmission matrix. From the mesoscopic transport literature, it is known that the conductivity of these disordered quasi-1D wires is affected by weak localization, a reciprocity-induced phenomenon. In RICOTTA, we plan to break reciprocity by placing the samples in a magnetic field to induce Faraday effect. This will provide new insights into the transport properties, in addition to the results obtained by measuring other properties such as sample length, number of modes, or disorder intensity. The samples will be characterized by measuring the complete transmission matrix, paving the way for coherent wave control in such systems.

Quantum metrology is one of the most promising applications of quantum technologies, enabling the measurement of physical quantities with unprecedented accuracy and precision compared to techniques based on classical resources. For applications in biology and chemistry, the major interest in quantum metrology is focused on photonic systems. Indeed, photons can penetrate aqueous media, they do not damage fragile biological specimens and disturb them little while ensuring an efficient interaction with the environment. The exploitation of quantum photonics to develop a new generation of chemical sensors is particularly interesting as it would allow ultra-sensitive detection schemes and non-destructive measurements. Harnessing this technology for developing novel quantum sensor scenarios is an appealing opportunity that would enable ultra-sensitive detection schemes and non-destructive measurement. This is further facilitated by the progress in the fabrication, miniaturization, and integration of quantum photonics blocks using quantum integrated photonics platforms. These platforms enable high stability and accuracy, extended dynamic range, compact footprint, and low cost. Hence, the development of technological platforms and techniques for the generation and manipulation of quantum photonic states on-chip, and their interaction with the biological or chemical analyte is of significant importance, enabling in-situ, fast, selective, remote, real-time, and non-destructive sensing. However, the implementation of such physical systems still stands as an ambitious task with several technological roadblocks that hinder the full potential of the quantum metrology. In this context, PARADIS aims at demonstrating a disruptive hybrid technology platform that fulfils the promise of quantum metrology to deploy biosensors with sensitivity beyond the standard quantum limit in a compact and reliable system. The ambition is to develop a new generation of high-sensitivity quantum sensors integrated in a functionalized photonic chip. The envisaged technology is based on a hybrid photonic platform, composed of two complementary materials, lithium niobate and laser-written glass, respectively well known for their exceptional non-linear properties and their flexibility. The scientific objective is to develop an integrated quantum sensor to detect chemical species. In this project, we will focus on detecting a gas, CO2, in order to provide a proof of principle. We pay attention to the general view of this project because we will focus on demonstrating the basic principles that can be adapted to the target species (chemical or biological). The principle of the experiment is based on two-photon interferometry by exploiting the properties of entanglement. On the other hand, PARADIS takes up technological challenges in order to develop high quality integrated components, with the vision of gathering a myriad of functions in a single photonic chip allowing both the generation and the manipulation of quantum resources. PARADIS will enable new innovations in interferometry, making it possible to realize quantum devices at the chip scale, enabling the deployment of laboratory techniques for practical use. This project will contribute to the long-term development of new technological capabilities by bridging quantum technologies to use cases.

Lithium niobate (LN) is a material very exploited in photonics circuits (optical frequency generators, phase or intensity modulators, quantum states generators…) from labs use to satellites embedded devices. LN thin-films (LNOI) revolutionized integrated optics: by decreasing by several orders of magnitude the control voltage and increasing the modulation rate in intensity modulators, or enhancing frequency generators efficiency. However, the wafers substantial cost, the number and complexity of technological steps for manufacturing circuits, as well as their limited compatibility with standard fiber components (injection losses of several decibels) represent a bottleneck for further development of this technology. In the current project, we propose to combine processes well-known and mastered by the team members to fill the gap between standard photonics chip on bulk LN and LNOI based chips. The goal will be to fabricate a substrate, and components, approaching the outstanding results obtained with LNOI while reducing its fabrication complexity, using low-cost techniques: a layer of increased refractive index will be induced on the surface of a standard LN using a technique perfectioned in INPHYNI since 2013. Several methods of waveguides creation will be implemented: etching of the substrate or of a guiding deposited layer by mechanical or plasma. We will also combine our skills in numerical simulation and technology to keep a high compatibility of the waveguides with fiber-devices. As the originality of the project lies in the compatibility of the processes rather than in their technicality, the risks are low, and for each step we plan several backup solutions in case of failure.

In WAQUAM, a new generation of photonic quantum memory architecture will be developed, in order to allow for high performance on-demand storage of quantum information. Such devices are of central importance for the development of quantum networks, in which quantum information is generated, manipulated, stored, transmitted and detected. In these networks, synchronization capability is crucial for high-rate information exchange. The device will be designed as a ridge waveguide, shaped within a rare-earth ion-doped crystal: praseodymium-doped yttrium orthosilicate. By combining unprecedented coherence properties of rare-earths with a non-invasive waveguide fabrication technique, similar performances compared to state-of-the-art bulk implementation will be witnessed for the first time. Moreover, the hybrid design will enable for the first time the integration of multiple active functions on the same device, by allowing photonic routing in the silica substrate. Heterogeneous bonding techniques combined with mechanical dicing will permit the fabrication of the waveguides, which will demonstrate state-of-the-art optical performances. On-demand storage of photonic quantum superposition at the single photon level will then be demonstrated in the on-site fabricated devices thanks to the atomic frequency comb protocol, qualifying them as a full-fledged photonic platform for quantum technologies. Local expertise at INPHYNI regarding waveguide fabrication and characterization both in the classical and quantum regimes will give the project a solid environment towards its success.