Les interactions entre les excitons, particules bosoniques composées d'un électron et d'un trou liés par l'interaction coulombienne, et les photons sont grandement améliorés dans les guides d'ondes où la lumière est confinée par réflexion totale interne. Lorsque l’interaction est suffisamment importante, le régime de couplage fort entre le mode photonique du guide et la résonance excitonique de la couche active est atteint, créant ainsi une quasi-particule connue sous le nom d'exciton-polariton, ou simplement polariton. Ces fluides quantiques de lumière suscitent un grand intérêt en raison de leur potentiel d'applications en optoélectronique, en particulier dans les lasers dits à polaritons. Dans cette optique, cette thèse se focalise sur l’étude, par des méthodes de spectroscopie, de structures lasers à polaritons en géométrie guide d’onde à base de nitrure de gallium (GaN), qui présentent des spécificités intéressantes en comparaison de leurs homologues en géométrie de cavité verticale intensément étudiées. Les principaux résultats de ce travail sont (i) la démonstration d'un laser à polaritons fonctionnant en régime continu à basse température (70K). Ce laser présente un mode de fonctionnement original, qui résulte de la non-réciprocité entre absorption et émission stimulée dans la couche active. Le gain significatif permet un fonctionnement efficace sur des cavités très courtes, comme celles de 20μm utilisées dans cette étude. De plus une longueur de pompe de seulement 15% de la longueur de cavité suffit pour atteindre l’effet laser, ce qui distingue clairement ces lasers à polaritons des lasers semi-conducteurs conventionnels exigeant un pompage d'une grande partie de la cavité laser par un milieu actif homogène pour que le gain l’emporte sur les pertes ; (ii) l'observation, en étendant notre étude à T=150K, d'une transition de régime laser avec un caractère multimode sur une cavité plus longue de 60µm. La modélisation des spectres mesurés permet de conclure que cette émission est impulsionnelle, grâce à la formation de solitons de cavité par un blocage de modes induit par les interactions non-linéaires entre les polaritons ; (iii) des mesures préliminaires d’injection électrique dans des guides d’onde avec couches d’injection dopées, suite à la mise en place d'un nouveau dispositif expérimental d'électroluminescence indépendant de celui de la spectroscopie optique.

In this work, we analyze the near-field radiative heat transfer (NFRHT) between finite-thickness planar fused silica slabs coated with graphene gratings. We go beyond the effective medium approximation by using an exact Fourier modal method equipped with specific local basis functions, and this is needed for realistic experimental analysis. In general, coating a substrate with a full graphene sheet has been shown to decrease the NFRHT at short separations (typically for d < 100 nm) compared to the bare substrates, where the effective medium approximation consistently overestimates the radiative heat flux, with relative errors exceeding 50%. We show that by patterning the graphene sheet into a grating, the topology of the plasmonic graphene mode changes from circular to hyperbolic, allowing to open more channels for the energy transfer between the substrates. We show that at short separations, the NFRHT between slabs coated with graphene gratings is higher than that between full-graphene-sheet coated slabs and also than that between uncoated ones. We also exhibit a significant dependence of the radiative heat transfer on the chemical potential, which can be applied to modulate in situ the scattering properties of the graphene grating without any geometric alterations. Additionally, we compare the exact calculation with an approximate additive one and confirm that this approximation performs quite well for low chemical potentials. This work has the potential to unveil new avenues for harnessing non-additive heat transfer effects in graphene-based nanodevices.

We experimentally demonstrate polariton laser in a GaN ridge waveguide. The strong-coupling regime is assessed through a comparison of the measured and modeled cavity free spectral range (FSR). The findings reveal that the laser exhibits a transition from monomode to multimode operation as the temperature is increased from 70K to 150K. The transition to multimode lasing is characterized by a flattening of the FSR just above the threshold, which constitutes the signature of mode synchronization induced by polaritonic nonlinearities.

Although AI-enabled customer relationship management (CRM) systems have gained momentum in healthcare to enhance performance, there is a striking dearth of knowledge on how such capabilities are formed and affect service innovation. The study adopted a mixed-method approach to investigate the underlying phenomena. This research infused resource-based theory, dynamic capability theory, and theory of productivity paradox to investigate how healthcare in India acquires AI-enabled CRM capabilities and enhances service innovation. We identified the facets of AI-enabled CRM capabilities using a case study and developed a framework for AI-enabled CRM capability and service innovation. This study noticed that customer service flexibility (CSF) is a missing link in this relationship. The findings of the quantitative study employing PLS-SEM reveal the linear relationships between AI-enabled CRM capability, CSF, and service innovation. This study explains the formation of AI-enabled CRM capabilities to fill the research gap and direct innovative performance in healthcare, which is an immediate need to sustain in a volatile environment. This study provides theoretical implications to enhance the research stream and practical implications for decision-makers. \textcopyright 2022 Elsevier Ltd

The boron-vacancy spin defect (V − B) in hexagonal boron nitride (hBN) has a great potential as a quantum sensor in a two-dimensional material that can directly probe various external perturbations in atomic-scale proximity to the quantum sensing layer. Here, we apply first principles calculations to determine the coupling of the V − B electronic spin to strain and electric fields. Our work unravels the interplay between local piezoelectric and elastic effects contributing to the final response to the electric fields. The theoretical predictions are then used to analyse optically detected magnetic resonance (ODMR) spectra recorded on hBN crystals containing different densities of V − B centres. We prove that the orthorhombic zero-field splitting parameter results from local electric fields produced by surrounding charge defects. By providing calculations of the spin-strain and spin-electric field couplings, this work paves the way towards applications of V − B centres for quantitative electric field imaging and quantum sensing under pressure.