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Currently, there are no cheap and compact sources in the mid-infrared range that can be modulated at high frequencies. Incandescent sources such as hot membranes and globars are widely used for mid-infrared spectroscopic applications, but for detection or communication applications where fast temperature modulation are desirable, thermal inertia quickly becomes a limiting factor. Besides, such incandescent sources are typically unpolarized, isotropic, broadband and have a low efficiency. However, these properties are not imposed by fundamental limitations stemming from physics laws, except for the low brightness dictated by Bose-Einstein distribution. Here, we introduce a metasurface that combines nanoscale heaters to ensure fast thermal response and nanophotonic resonances to provide large spectrally selective and polarized emissivity. We report a peak emissivity of 0.8 and an operation up to 20 MHz, six orders of magnitude faster than commercially available hot membranes.

International audience; In the last decades, designs of most incandescent sources have been realized by heating the whole device. Here we propose a novel approach consisting in taking advantage of hot nanoemitters that can be cooled in a few tens of nanoseconds. It offers a new opportunity for high speed modulation and for enhanced agility in the active control of polarization, direction and wavelength of emission. To compensate the weak thermal emission of isolated nanoemitters, we propose to insert them in some complex environments, such as e.g. the gap of cold nanoantenna, which allow a significant thermal emission enhancement of the hot nanovolume. In order to optimize this kind of device, a fully vectorial upper bound for the thermal emission of a hot nanoparticle in a cold environment is derived. This criterion is very general since it is equivalent to an absorption cross-section upper bound for the nanoparticle. Moreover, it is an intrinsic characteristic of the environment regardless of the nanoparticle, so it allows to decouple the design of the environment from the one of the hot nanovolume. It thus provides a good figure of merit to compare the ability of different systems to enhance thermal emission of hot nanoemitters.

International audience; We study light absorption by a dipolar absorber in a given environment, which can be a nanoantenna or any complex inhomogeneous medium. From rst-principle calculations, we derive an upper bound for the absorption, which decouples the impact of the environment from the one of the absorber. Since it is an intrinsic characteristic of the environment regardless of the absorber, it provides a good figure of merit to compare the ability of different systems to enhance absorption. We show that, in the scalar approximation, the relevant parameter is not the field enhancement but the ratio between the field enhancement and the local density of states. Consequently, a plasmonic structure supporting hot spots is not necessarily the best choice to enhance absorption. We also show that our theoretical results can be applied beyond the scalar approximation and the plane-wave illumination.

International audience; In recent decades, researchers have demonstrated incandescent sources that exhibit monochromatic, directional, and even fast modulated infrared emission. Most of the researchers achieve this type of emission by heating the whole device. Here, we propose heating only nanovolumes that can be cooled in a few tens of nanoseconds. This approach could enable high-speed modulation. To compensate for the weak thermal emission of such isolated nanoemitters, we propose inserting the hot nanovolume in the gap of a cold nanoantenna. We calculate the resulting emission enhancement by using a generalized version of Kirchhoff's law, and demonstrate that careful design of the complete antenna– nanoemitter system can result in emission enhancements of more than four orders of magnitude.

International audience; Light emission by ensembles of emitters can be tailored using resonators such as cavities or plasmonic antennas. While concepts such as field enhancement, Purcell effect, and quenching can be used to understand the interplay between a two‐level system and a resonator, they fail to account for light emission by ensembles of emitters. Recent experiments reporting light emission by thermalized molecules, quantum dots, and hot electrons excited optically or electrically are reviewed. It is shown that the local Kirchhoff's law provides a unified framework to discuss photoluminescence, electroluminescence, and thermal radiation by ensembles of thermalized emitters coupled to resonators.