This page contains 11 PhD proposals.
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After more than 40 years of continuous evolution, our computing systems are reaching their limits. Indeed, the architecture of Von-Neumann, on which our computers are based, physically dissociates the hearts of calculations from the memory. The sequential processing of information is thus confronted with a bottleneck, more commonly known as "Memory Bottleneck". One solution is to draw inspiration from the natural mathematical paradigms of the human brain, in which the data are massively parallel processed with high energy efficiency, realizing the hardware implementation of neuromorphic networks. The latter make it possible to bring the information storage sites (synapses) closer to the treatment sites (neurons). The major challenge of this bio-inspired approach is the realization of dense networks of artificial synapses to implement synaptic plasticity mechanisms.

The Mid-infrared (Mid-IR) wavelength range - from 2.5 to 13 µm - is currently experiencing a huge surge in interest for an enormous range of applications that affect almost every aspect of our society, from compact and highly sensitive biological and chemical sensors, imaging, defense and astronomy. A notable feature of the Mid-IR is that most chemical and biological compounds that relate to our health, safety and environment have a strong spectral signature in this spectral range. The Mid-IR therefore offers unique opportunities for the development of technologies with a high societal (sensor applications, defence, industrial and environmental security, etc.) and fundamental impact (chemistry, biology, astrophysics, etc.). Many actors in the nanophotonics scene have invested in this theme in the USA (Air Force research lab, Harvard, UCLA, Princeton MIRTHE, IBM, Cornell etc...), Australasia and Europe (INL, C2N, University of Surrey, Southampton, University of St Andrews, Ghent/IMEC).

It is well established that photons are suitable for communication and electrons for computing. Yet the border between computing and communication has become somehow blurred when considering emerging research domain such as optical interconnects and photonic neuromorphic computing. In many contexts it has been realized that photonics can help computation by providing an efficient interface for short-distance communication or for performing simple operations but in a massively parallel fashion. Here we consider the problem of dealing with high-speed signals in the optical domain needing to be digitized with very high accuracy. This PhD project will address the most critical operation here, namely extremely accurate sampling with minimal timing error.

The Mid-infrared (Mid-IR) wavelength range - from 3 to 15 µm - is currently experiencing a huge surge in interest for an enormous range of applications that affect almost every aspect of our society, from compact and highly sensitive biological and chemical sensors, imaging, defense and astronomy. A notable feature of the MIR is that most chemical and biological compounds that relate to our health, safety and environment have a strong spectral signature in the medium infrared. The MIR therefore offers unique opportunities for the development of technologies with a high societal (sensor applications, defence, industrial and environmental security, etc.) and fundamental impact (chemistry, biology, astrophysics, etc.).

Strongly resonant (high-quality Q factor) resonators represent an essential element in photonics, for exploring the fundamental aspects of light-matter interaction , as well as for applications in filtering, wavelength demultiplexing, sensing and, combined with an active or nonlinear material, generation of light. High-Q micro-cavities in the mid-IR have been introduced only recently and the topic remains very challenging, in particular when integrating them with a photonic platform amenable to lasing. Such a platform would enable high-purity sources for sensitive detection in this spectral range based on heterodyne detection.

The development of an ion-sensitive semiconductor device that combines the principles of a MOS transistor and a glass reference electrode was proposed by Bergveld in 1970. Commonly called ISFET, this device measures ionic activities in electrochemical or biological environments. The ISFET type pH sensors have a sensitive dielectric layer on which the electrolyte will be deposited. Several dielectrics can be used: SiO2, Si3N4, Al2O3, SnO2, Ta2O5 [Matsuo 81]. This type of sensor used for 30 years since the first demonstration of ISFET has a maximum sensitivity limited to ambient temperature of 59.6 mV / pH. More recently, different approaches have demonstrated increased sensitivities that exceed this limit, called the Nernst limit. Parizi reached 130 mV / pH with a circuit comprising two sensors, each with a field effect transistor and an enlarged sensitive grating. They achieved these performances by capacitively coupling a floating gate of a MOSFET with an ion sensitive gate which is remote from the gate of the transistor. Even greater sensitivities were also achieved using double grid ISFETs: Jang used a dual ultra-thin body (UTB) grid to reach 426 mV / pH, while Huang reached 453 mV / pH using the best electrostatic control of the channel with both grids.

Circulating tumor cells (CTCs) play an important role in metastasis dissemination. CTCs are tumor cells that separate from the tumor and join the bloodstream. They are characteristic of the tumor from which they shed. In these last decades, the count of CTCs from total blood has been clearly associated with bad prognosis in many cancer types. In particular, CTC-clusters demonstrate increased metastatic potential compared to single CTCs and their presence is strongly correlated with a dramatically shorter overall survival time. Thus, baseline CTC counts and monitoring of CTCs numbers under treatment is a prognostic factor of survival. However, since CTCs are rare cells (some CTCs for millions of blood cells) their capture remains challenging. Moreover, in order to study the metastatic power of these CTCs and to test their chemosensitivity towards new molecules, it is necessary to capture them alive, to cultivate them in dedicated micro-environments and to analyze their secretions in various conditions. Microfluidic devices are a proven technology for cellular handling as they can offer precise spatial and temporal control in a miniaturized environment compatible with cell or cell cluster size. This approach is particularly suitable for rare cell manipulation and multiplex biosensor technology that will allow the real-time detection of cell secretions.

Breast cancer is the second most common cancer diagnosed worldwide, so it still remains a major public health problem. 90% of breast cancer-related deaths are caused by distant metastases. Thus, disseminated malignancy remains one of the main diagnostic and therapeutic challenges today. However, early dissemination of tumour cells is usually undetectable in patients by conventional histopathology, molecular and imaging techniques. Numerous cancer biomarkers have been identified. Among them, serum circulating cancer biomarkers (CCB) (tumor proteins and circulating miRNA) are promising biomarkers for cancer prognosis and treatment monitoring. Currently, the detection of these biomarkers (qPCR, ELISA, MS, etc.) remains time and sample-consuming, expensive and complex, which difficult their analysis in a clinical routine basis. In this regard, biosensors stand out as promising technology solutions for CCB detection due to their selectivity, sensitivity, and their capabilities for miniaturization for the development of simple-to-use Lab-on-chip and Point-of-care devices. Biosensors can be designed to provide quantitative analytical information with elevated accuracy in a few minutes, using low sample volumes and minimum sample pre-treatment. Recent breakthroughs in integrated circuit technology have led to the creation of new types of biosensors based on photonics showing very low limits of detection ...

2D materials such as phospherene black phosphorus thin layer) or Molybdenum oxide are envisioned to be used into nanodevices such as nanolasers or nanosensors. For example the band gap of phosphorene gap can be adjusted from 0.2 to 1.2eV. Therefore, its optoelectronic properties are expected to be easily tunable, thus providing a powerful versatility for creating new nanodevices. However the experimental integration of such material in sensors architecture, and experimental surface functionalization is currently reported only in a few articles. In order to concretize sensors involving such 2D materials, it is necessary to explore how to modify their surface chemistry, in order to graft molecular probes while preserving their optoelectronic properties.

The combination of several materials on the surface of a nanoparticle is of great interest in the field of catalysis. In particular, the immobilization of gold or platinum nanocatalyzers on oxide nanoparticles allows increasing their efficiency, because oxidation reactions are preferentially achieved onto oxygen vacancies. It also avoids nanocatalyzers aggregation and improves their stability. Nanozymes are hybrid nanoparticles with catalytic properties that can mimic the behaviour of natural enzymes. It was recently shown that nanozymes can be used as ultrasensitive and ultrafast biosensors able to detect target molecules with a concentration as low as 0.1 ppm and in few minutes, using aptamers as bioreceptors. The presence of aptamers onto nanoparticles surface blocks the enzymatic oxidation. When biological target is injected, aptamers leave the surface to engage with the target and the enzymatic oxidation is restored. Using the specificity of aptamers, any kind of biological target (oligonucleotides, proteins, cells, bacteria) could be detected.

In the past two decades, silicon photonics has emerged as a mature technological platform allowing for multiple optical functions to be integrated onto the same chip. Electro-optic modulators, SiGe photodetectors and low-loss silicon waveguides are now available. However, when it comes to light emission or nonlinear functions, silicon turns out to be intrinsically limited. The heterogeneous integration of III-V materials onto silicon has already provided a way to realize efficient LED or laser devices. Similarly, several material candidates are investigated for their nonlinear properties, with the aim to integrate them onto the mature silicon photonic platform. The nonlinear optical response of materials can sustain the realization of optical devices such as all-optical switches and even amplifiers that can directly control light signals with other light signals. These can be much faster than in their optoelectronic counterparts. Perhaps more importantly, these nonlinear properties can enable completely new functions such as wavelength conversion, the generation of frequency combs or supercontinuum pulses. More generally, a wide range of nonlinear devices can be realized for information processing using light control signals. These could advantageously complement the power-hungry and bulky electronic routers that are used in telecommunications. These routers perform data processing and signal routing in the electrical domain, i.e. after converting light signals that convey information across the Internet network. They already struggle to cope with the exponentially increasing data flows across the internet, calling for the need to develop alternative and disrupting technologies. All-optical devices could play a central role there.

Point-like defects in wide-bandgap materials are attracting intensive research attention owing to prospective applications in quantum technologies (information processing, sensing) and in near infrared spectrum bio-imaging. The reason is three-fold: (i) these defects can be considered as artificial atoms with highly efficient optical transitions (single photon sources realization); (ii) they may encompass charge, orbital and spin degrees of freedom, with possibility for instance of optical control of the spin (Qubit application); (iii) the spin and electronic states can be well isolated from environmental fluctuations leading to record spin coherence. In this context, the nitrogen-vacancy (NV) center in diamond has become a highly mature system, used for a large range of applications. Nevertheless, since 2010, point defects in SiC have been intensively studied. Indeed, SiC presents advantages for these applications: (i) growth at an industrial scale ; (ii) control of the technological steps for devices realization thanks to the upstream of power electronic applications ; (iii) unparalleled properties making SiC an ideal platform for photonic quantum information processing.

The I3E ECLAUSion project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 801512