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Securing communications over long distances requires bright single photon sources emitting in the telecom band in a well-defined spatial and polarization mode. First, we report our efforts to obtain single photon emission and a Gaussian far-field radiation pattern in the telecom O-band from single quantum dot-nanowires (QD-NWs) monolithically grown on silicon. The InAs/InP QD-NWs were grown on silicon (111) substrates by Vapor-Liquid-Solid assisted solid-source Molecular Beam Epitaxy using In-Au droplets as a catalyst in-situ deposited at 500°C [1]. Low QD-NW density was obtained by a careful control of the In/Au catalyst flux ratio to achieve density <1 NW/μm² [2]. The growth conditions have been tuned (Fig 1.a) to optimize the source brightness and reduce the far-field divergence. The control of the nanowire geometry allows us to demonstrate a Gaussian far field emission profile with an emission angle θ≈30° (Fig 1.c) from a single QD at room temperature in the telecom O-band and the observation of single photon emission with g2(0) = 0.05 (Fig 1.b) at cryogenic temperature [3]. Secondly, we have optimized the growth procedure to achieve InAs/InP QD NWs with an elongated top-view cross-section. Polarization-resolved photoluminescence measurements have revealed a significant influence of the asymmetric shaped NWs on the InAs QD emission polarization with the photons being mainly polarized parallel to the NW long cross section axis [4]. A degree of linear polarization (DLP) up to 91% is obtained, being at the state of the art for the reported DLP values from QD-NWs.\\References:[1] A. Mavel et al, Journal of Crystal Growth, 458 (2017) 96.[2] A. Jaffal et al, Nanotechnology, 31 (2020) 354003.[3] A. Jaffal et al, Nanoscale, 11 (2019) 21847-21855.[4] A. Jaffal et al, Nanoscale, 13 (2021) 16952–16958.

DOI: 10.1016/j.mtphys.2023.101207
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Graphene, as a two-dimensional magneto-optical material, supports magnetoplasmon polaritons (MPP) when exposed to an applied magnetic field. Recently, MPP of a single-layer graphene has shown an excellent capability in the modulation of near-field radiative heat transfer (NFRHT). In this study, we present a comprehensive theoretical analysis of NFRHT between two multilayered graphene structures, with a particular focus on the multiple MPP effect. We reveal the physical mechanism and evolution law of the multiple MPP, and we demonstrate that the multiple MPP allow one to mediate, enhance, and tune the NFRHT by appropriately engineering the properties of graphene, the number of graphene sheets, the intensity of magnetic fields, as well as the geometric structure of systems. We show that the multiple MPP have a quite significant distinction relative to the single MPP or multiple surface plasmon polaritons (SPPs) in terms of modulating and manipulating NFRHT. We demonstrate that this remarkable behavior is attributed to the coupling between the significant contributions of surface states at multiple surfaces and Shubnikov–de Haas-like oscillations in the spectrum, indicating a transformation of intraband and interband transitions. Notably, we find that the evolution from single MPP to multiple MPP is absolutely different from that from single SPPs to multiple SPPs. Finally, a thermal magnetoresistance effect and a negative-positive transition of the relative thermal magnetoresistance ratio are predicted in the multilayered system under consideration. Our study paves the way for a flexible control of NFRHT and it offers the possibility for the thermal photon-based communication technology and a magnetically controllable thermal switch.

DOI: 10.1039/d3cp01912h
Résumé:

As an analogue to an electrical diode, a radiative thermal diode allows radiation to transfer more efficiently in one direction than in the opposite direction by operating in a contactless mode. In this study, we demonstrated that within the framework of three-body photon thermal tunneling, the rectification performance of a three-body radiative diode can be greatly improved by bringing graphene into the system. The system is composed of three parallel slabs, with the hot and cold terminals of the diode coated with graphene films and the intermediate body made of vanadium dioxide (VO2). The rectification factor of the proposed radiative thermal diode reaches 300% with a 350 nm separation distance between the hot and cold terminals of the diode. With the help of graphene, the rectification performance of the radiative thermal diode can be improved by over 11 times. By analyzing the spectral heat flux and energy transmission coefficients, it was found that the improved performance is primarily attributed to the surface plasmon polaritons (SPPs) of graphene. They excite the modes of insulating VO2 in the forward-biased scenario by forming strongly coupled modes between graphene and VO2 and thus dramatically enhance the heat flux. However, for the reverse-biased scenario, the VO2 is at its metallic state, and thus, graphene SPPs cannot work by three-body photon thermal tunneling. Furthermore, the improvement was also investigated for different chemical potentials of graphene and geometric parameters of the three-body system. Our findings demonstrate the feasibility of using thermal-photon-based logical circuits, creating radiation-based communication technology and implementing thermal management approaches at the nanoscale.

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DOI: 10.1039/D3CP03706A
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We study within the framework of the Lifshitz theory the long-range Casimir force for in-plane isotropic and anisotropic free-standing transdimensional material slabs. In the former case, we show that the confinement-induced nonlocality not only weakens the attraction of ultrathin slabs but also changes the distance dependence of the material-dependent correction to the Casimir force to go as $\sim\!1/\!\sqrt{l}$ contrary to the $\sim\!1/l$ dependence of that of the local Lifshitz force. In the latter case, we use closely packed array of parallel aligned single-wall carbon nanotubes in a dielectric layer of finite thickness to demonstrate strong orientational anisotropy and crossover behavior for the inter-slab attractive force in addition to its reduction with decreasing slab thickness. We give physical insight as to why such a pair of ultrathin slabs prefers to stick together in the perpendicularly oriented manner, rather than in the parallel relative orientation as one would customarily expect.

Ref HAL: hal-04172452_v1
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We present an accurate and simple semi analytical model for studying the magneto- plasmonic response of a 1D subwavelength graphene strip grating under an external static mag- netic field. In this model, the graphene sheet is considered as an anisotropic layer with atomic thickness. Under these conditions and in contrast to the previous works, an effective medium approach (EMA) is applied to the graphene permittivity tensor and a rigorous phase correction is required to take into account the periodicity effect. The resonance phenomena occurring into the structure are taken into account in the model using the scattering matrix approach. The re- flection and transmission spectra of the structure are then given as the sum of two contributions, the scattering contribution and the single strip contribution. In order to numerically validate and evaluate the proposed model, the results have been compared with those obtained from the PMM [1, 2] method and from methods published in the literature [3, 4]. This simple approach is useful to better understand graphene surface magnetoplasmons GSMPs and may facilitate the design of various tunable devices based on graphene magnetoplasmonics.

Ref HAL: hal-04172425_v1
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In this work, we propose a novel hybrid magneto plasmonic structure based on graphene and doped InSbto enhance the magneto optical Kerr effect at terahertz frequencies.The structure is composed of a 1D periodic dopedInSb inlayed between a metallic backgate and a dielectric/doped graphene sheet .By computing the optical responseof this structure, w e show an enhanced and large Kerr rotation in a wide range of THz frequencies compared to thatinduced by a single graphene sheet and/or a doped magnetized InSb

Ref HAL: hal-04172392_v1
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Design of the metallic contact grid at the front side of thermophotovoltaic cells is critical. Our study, based on a rigorous approach, investigates the real influence of the front metal contact grid. By modelling this grid by a metallic grating, we show that it can significantly affect the electrical power generated by the cell. Quantitative and qualitative analyses indicate behaviors which are quite different from those predicted by previous simplistic approaches.