We demonstrate, experimentally and theoretically, a universal mechanism for combining nanophotonic modes relying on radiative-loss-mediated couplings. For the case of two modes this mechanism leads to a BIC-type phenomenon characterized by the emergence of a high-quality factor subradiant mode. This mode is experimentally observed in the mid-infrared range, in arrays of double-metal patch antennas where the radiation loss rates are controlled by the geometry of the system. As the mechanism described here is independent of the specific nature or number of the interacting modes, it can be used to combine physically different resonating structures, without requiring fine symmetry tuning or specific modal configurations, opening new opportunities for resonance-based nanophotonic devices.

Correlated disorder is known to shape light scattering in ways uncorrelated disorder cannot, from hyperuniform transparency to the structural colors of naturally occurring structures. What has been missing in photonics is a direct link between the disorder and the scattering pattern it produces. Here we show that adding correlated noise to a periodic array splits the scattering pattern into three distinct components: diffraction peaks, a diffuse background, and correlation halos. Often mistaken for broadened diffraction peaks, these halos are in fact independent features: their positions are set by the correlation range, meaning that they can appear between Bragg peaks, and - crucially - they persist far beyond the regime where the diffraction peaks vanish. Shaping the disorder itself offers further control: tuning the noise distribution suppresses selected diffraction peaks, while tuning the correlation statistics moves the halos away from the Bragg positions. This approach reproduces the scattering signatures of natural photonic structures, such as Morpho butterfly wings, and reveals multiple pathways from order to disorder, each with distinct optical properties. It also offers a practical route to inverse design - finding the disorder that produces a desired scattering pattern. This establishes scattering as a designable quantity, expanding the toolkit for metasurfaces and structural colors.

Helmholtz optical cavities have recently emerged as promising platforms for enhancing light–matter interactions at subwavelength scales. There resonance have been successfully exploited in the infrared for broadband molecular detection using Surface Enhanced InfraRed Absorption (SEIRA) spectroscopy. In this work, we extend the concept to the terahertz (THz) range, introducing a Helmholtz resonator architecture tailored for Surface-Enhanced Terahertz Absorption (SETA). Such resonators are designed to operate in the over-coupled regime, where reflectivity remains non-zero, but can transition toward critical coupling upon the introduction of an absorbing analyte. This change leads to a measurable reflectivity contrast that can be exploited for molecular sensing. We present both simulated and experimental results demonstrating the interaction between the resonator and thin layers of 2,4-dinitrotoluene (2,4-DNT). Numerical results show a reflectivity contrast of up to 20% as a function of analyte thickness. Experimental measurements on fabricated samples confirm the resonance behavior and the expected contrast.

Imaging in the Terahertz (THz) is an active field of research that finds numerous applications such as non-destructive industrial testing, security or chemical identification. However, the high cost and low sensitivity of terahertz detectors constitute a serious obstacle for a wide range of applications. In this context, exalted thermal conversion in metasurfaces promises to be a cost effective alternative technique. In this talk, I will present nanostructured ultra-thin PET membranes that are designed to absorb the THz wave and effectively heat up thus emitting in the infrared.First, we image the heat transfers in the terahertz metasurface from the first time of heating up to the steady states and compare it to finite element modelling coupling electromagnetic and thermal physics. Interestingly, the THz metasurface is easily resolved through an infrared camera leading to the demonstration of far field acquired image of the near field modes of the metasurface. Then, we characterize the convection and conduction impact on the membrane efficiency and response time in order to design an optimized printed split-ring resonator based membrane for the imagery of a THz focused beam.

Under high electrical current, some materials can emit electromagnetic radiation beyond incandescence. This phenomenon, referred to as electroluminescence, leads to the efficient emission of visible photons and is the basis of domestic lighting devices (for example, light-emitting diodes)1,2. In principle, electroluminescence can lead to mid-infrared emission of confined light-matter excitations called phonon polaritons3,4, resulting from the coupling of photons with crystal lattice vibrations (optical phonons). In particular, phonon polaritons arising in the van der Waals crystal hexagonal boron nitride (hBN) present hyperbolic dispersion, which enhances light-matter coupling5,6. For this reason, electroluminescence of hyperbolic phonon polaritons (HPhPs) has been proposed as an explanation for the peculiar radiative energy transfer within hBN-encapsulated graphene transistors7,8. However, as HPhPs are locally confined, they are inaccessible in the far field, and as such, any hint of electroluminescence has been based on indirect electronic signatures and has yet to be confirmed by direct observation. Here we demonstrate far-field mid-infrared (wavelength approximately 6.5 μm) electroluminescence of HPhPs excited by strongly biased high-mobility graphene within a van der Waals heterostructure, and we quantify the associated radiative energy transfer through the material. The presence of HPhPs is revealed by far-field mid-infrared spectroscopy owing to their elastic scattering at discontinuities in the heterostructure. The resulting radiative flux is quantified by mid-infrared pyrometry of the substrate receiving the energy. This radiative energy transfer is also shown to be reduced in hBN with nanoscale inhomogeneities, demonstrating the central role of the electromagnetic environment in this process.

Fabry–Perot (FP) resonances are ubiquitous in plasmonic resonators; however, their quality factor is mostly driven by the losses of the material and has a typical value of 10 for noble metals. The coupling of two FP nanocavities (cFP) was theoretically shown by Opt. Lett. 42 , 5062 ( 2017 ) 10.1364/OL.42.005062 to enable the control of the quality factor, thanks to a geometrical parameter. Here, we experimentally demonstrate in the infrared range the cFP resonance with a quality factor of 30 in a structure made of metallic grooves with a trapezoidal-shaped profile that is simultaneously easier to fabricate and more complex to model. An analytical one-mode model is derived that undoubtedly attributes the resonance to the coupling of interferences between the two nanocavities. Finally, we also experimentally demonstrate the combination of two cFP either in orthogonal polarizations or for distinct wavelengths.

Effective cross-sections of nano-objects are fundamental properties that determine their ability to interact with light. However, measuring them for individual resonators directly and quantitatively remains challenging, particularly because of the very low signals involved. Here, we experimentally measure the thermal emission cross-section of metal-insulator-metal nano-resonators using a stealthy hyperuniform distribution based on a hierarchical Poisson-disk algorithm. In such distributions, there are no long-range interactions between antennas, and we show that the light emitted by the metasurface behaves as the sum of cross-sections of independent nanoantennas, enabling direct retrieval of the single resonator contribution. The emission cross-section at resonance is found to be of the order of $\mathbf{\lambda_0^2/3}$, a value that is nearly three times larger than the theroretical maximal absorption cross-section of a single particle but remains smaller than the maximal extinction cross-section. This measurement technique can be generalized to any single resonator cross-section, and we also apply it here to the extinction cross-section.

Effective cross-sections of nano-objects are fundamental properties that determine their ability to interact with light. However, measuring cross-sections for individual resonators directly and quantitatively remains challenging, particularly because of the very low signals involved. In this contribution, we present how we experimentally measured the thermal emission cross-section of metal-insulator-metal nano-resonators using a hyperuniform distribution based on a hierarchical Poisson-disk algorithm. This method relies on the specific properties of hyperuniform distributions, which ensure that no short-range or long-range correlations between resonators disturb the measured signal.

Metallic gratings can be used as infrared filters, but are limited by their narrow bandwidth due to metallic losses. Here, we propose a metallic groove-slit-groove (GSG) structure that exhibits an angularly independent extraordinary optical transmission of over 70% with a full spectral width at half maximum of 2 µm in the longwave infrared range. Each groove interferes with the central slit following a Fano profile, as confirmed by a pole study in the complex frequency plane. In addition, the two Fano profiles mirror each other, so that their association gives rise to a broadband transmission flanked by two zeros, improving the rejection rate. These results are extended to a two-dimensional GSG structure exhibiting unpolarized transmission of over 70%, for angles up to 50°.

Metasurfaces are engineered with specific shapes and sizes to interact with light in a unique way. By manipulating the design of the metasurface, it is possible to control optical properties of the surface such as its thermal emissivity. However, thin layers patterning techniques can lead to side-wall angles, thus modifying light propagation within the structure. Here, we introduce a one-mode model that fairly describes the propagation of light in structures with inclined sidewalls. We applied this method to two families of plasmonics resonators: nano Fabry-Perot and coupled nano Fabry-Perot with refractory materials ZrC and tungsten.

Detection of molecules is a key issue for many applications. Surface enhanced infrared absorption (SEIRA) uses arrays of resonant nanoantennas with good quality factors which can be used to locally enhance the illumination of molecules. The technique has proved to be an effective tool to detect small amount of material. However, nanoresonators can detect molecules on a narrow bandwidth so that a set of resonators is necessary to identify a molecule fingerprint. Here, we introduce an alternative paradigm and use low quality factor resonators with large radiative losses (over-coupled resonators). The bandwidth enables to detect all absorption lines between 5 and 10 μm, reproducing the molecular absorption spectrum. Counterintuitively, despite a lower quality factor, the system sensitivity is improved and we report a reflectivity variation as large as one percent per nanometer of molecular layer of PMMA. This paves the way to specific identification of molecules. We illustrate the potential of the technique with the detection of the explosive precursor 2,4-dinitrotoluene (DNT). There is a fair agreement with electromagnetic simulations and we also introduce an analytic model of the SEIRA signal obtained in the over-coupling regime.

Electroluminescence, a non-thermal radiative process, is ubiquitous in semi-conductors and insulators but fundamentally precluded in metals. We show here that this restriction can be circumvented in high-quality graphene. By investigating the radiative emission of semi-metallic graphene field-effect transistors over a broad spectral range, spanning the near- and mid-infrared, we demonstrate direct far-field electroluminescence from hBN-encapsulated graphene in the mid-infrared under large bias in ambient conditions. Through a series of test experiments ruling out its incandescence origin, we determine that the electroluminescent signal results from the electrical pumping produced by interband tunneling. We show that the mid-infrared electroluminescence is spectrally shaped by a natural quarter-wave resonance of the heterostructure. This work invites a reassessment of the use of metals and semi-metals as non-equilibrium light emitters, and the exploration of their intriguing specificities in terms of carrier injection and relaxation, as well as emission tunability and switching speed.

In this presentation we will discuss our efforts based on high sensitivity infrared microscopy and spectroscopy to unravel the origin of super-incandescent emission of high-mobility graphene transistors.

In this paper, we demonstrate experimentally record high SHG conversion efficiencies for broad-spectrum metal-insulator-metal metasurfaces in the infrared. The attained efficiencies reach the 10 -6 W -1 range, which is 22 times more than the previous ones.

Electromagnetic Helmholtz resonators are able to strongly and homogeneously enhance an electric field in relatively large volumes, making them attractive for applications to surface enhanced infrared absorption spectroscopy of molecules. We show in this study that such a structure, designed in the over-coupling regime can demonstrate strong enhancement of molecular modes of the polymer poly(methyl methacrylate) and the explosive molecule 2,4-dinitrotoluene over a very wide wavelength range between 5 and 10 µm. Reflectivity contrast provides access to the analyte’s absorption and quantitative information. Helmholtz-like resonators therefore offer a new platform for the creation of sensitive and versatile sensors.

Heat control is a key issue in nano-electronics, where new efficient energy transfer mechanisms are highly sought after. In this respect, there is indirect evidence that high-mobility hexagonal boron nitride (hBN)-encapsulated graphene exhibits hyperbolic out-of-plane radiative energy transfer when driven out-of-equilibrium. Here we directly observe radiative energy transfer due to the hyperbolic phonon polaritons modes of the hBN encapsulant in intrinsic graphene devices under large bias, using mid-infrared spectroscopy and pyrometry. By using different hBN crystals of varied crystalline quality, we engineer the energy transfer efficiency, a key asset for compact thermal management of electronic circuits.