Infrared near-field optics, micro and nano thermics

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We mainly study infrared radiation at sub-wavelength scales, whether resulting from thermal agitation or electrical pumping of a semiconductor or graphene-based device. We also study thermal transport at short scales. Our work ranges from fundamental research to applications. We collaborate with teams from academia, aerospace and industrial laboratories.

Applications to internships, PhD and positions are more than welcome (see “Jobs” section). For more information, please contact the group leader, Dr.Yannick De Wilde.
email:

Research topics

Electroluminescence and energy transfer in graphene transistors encapsulated in hBN

Electroluminescence is the emission of electromagnetic radiation beyond incandescence. It is generally known to occur at visible wavelengths in devices made of doped semiconductors.

In collaboration with Emmanuel Baudin’s team at LPENS (Ecole Normale Supérieure), we have detected mid-infrared radiation from high-mobility graphene transistors encapsulated in hexagonal boron nitride (hBN) subjected to a high bias voltage. We have shown that this infrared radiation results from the electroluminescence of hyperbolic phonon-polaritons excited by the recombination of graphene electrons beyond the Zenner Klein tunneling threshold. [Abou_Hamdan_NATURE2025].

Our studies have also shown that electroluminescence is concomitant with the onset of a highly efficient out-of-plane energy transfer process. This behavior had been predicted by the ENS team in 2018 on the basis of electrical transport measurements. [Yang_NATURE_NANOTECH2018].

Plasmonic and dielectric nano-antennas - Infrared spatial modulation spectroscopy

We have developed an infrared spatial modulation spectroscopy (IR-SMS) technique that can detect extremely weak thermal radiation signals without background noise, from objects whose dimensions are far smaller than the field of view of the infrared detectors used for Fourier transform infrared spectroscopy (FTIR).

In collaboration with Patrick Bouchon’s team at the French aerospace research center ONERA, we have applied this method to study the electromagnetic modes of individual metal-insulator-metal (MIM) antennas when excited by thermal fluctuations [Li_PHYS_REV_LETT2018]. We then studied the appearance of hybrid modes in dimers of near-field coupled MIM antennas. [Abou_Hamdan_OPT_LETT2021]. These studies are continuing, using NxN arrays of MIM antennas to create reconfigurable devices.

We have also applied the IR-SMS method to study the Mie resonances of silica microspheres (SiO2), which are of interest for daylight radiative cooling [Abou_Hamdan_ACS_PHOT2022].

Near-field radiative conductance: towards N-body systems

In collaboration with Wilfrid Poirier of the Laboratoire National de Métrologie et d’Essais (LNE), we have recently developed a probe that measures the near-field radiative conductance between a heated microsphere and a flat substrate from a separation of a few tens of micrometers down to a few tens of nanometers. This probe has already been used to measure thermal contact resistance [Doumouro_PHYS_REV_APPL2021]. We are currently pursuing these studies in order to observe radiative transfers between several objects in near-field coupling. This work is being carried out in collaboration with Philippe Ben-Abdallah and Riccardo Messina at Laboratoire Charles-Fabry-IOGS.

Thermal radiation on subwavelength scales

We study thermal radiation at distances far below the thermal wavelength (10 µm at room temperature). To carry out these studies, we have developed the TRSTM (thermal radiation scanning tunneling microscope), which enables us to measure thermal radiation at nanometric distances from the source. [De_Wilde_NATURE2006].

We were the first to obtain super-resolved images of near-infrared thermal radiation, corresponding to spatial variations in the local density of electromagnetic states (EM-LDOS).

We have also coupled the TRSTM to a Fourier Transform Infrared Spectrometer (FTIR) and demonstrated the non-Planckian spectrum of near-field thermal radiation associated with surface polaritons, which produce a quasi-monochromatic spectrum [Babuty_PHYS_REV_LETT2013]. This effect is responsible for an abnormal increase in short-distance heat exchange through near-field interaction.

TRSTM coupled with FTIR operates beyond the diffraction limit. It improves spatial resolution by a factor of 100 compared with infrared microscopes and spectrometers.

For example, the figure opposite shows the TRSTM study of the cleaved face of a multilayer stack of doped and undoped semiconductors, where each layer has a thickness of around 300 nm. In certain regions of the infrared spectrum, this stack behaves like a hyperbolic metamaterial. By measuring TRSTM images at different heights, we observed the transition from the homogeneous regime to one where the thermal radiation of each layer must be considered individually, over a distance of just 200 nm [Peragut_OPTICA2017].

The recording of spectro-images revealed the contribution to EM-LDOS of surface plasmons propagating at the interface between doped and undoped semiconductor layers.

Research linked with industrial partners

The skills acquired at the Institut Langevin in the field of small-scale thermics are of great interest to industry and the aerospace sector. We have recently begun collaborating with Saint-Gobain on the study of thermal insulation materials, and with ONERA on plasmonic antennas designed to improve the performance of infrared imagers. The image on the left shows a tomographic image of a fibrous insulation mat recorded by coherent optical microscopy (OCT), which we are studying using methods borrowed from nanoscience.

REFERENCES (full list here )

[Abou_Hamdan_NATURE2025] Electroluminescence and Energy Transfer Mediated by Hyperbolic Polaritons
L. Abou-Hamdan, A. Schmitt, R. Bretel, S. Rossetti, M. Tharrault, D. Mele, A. Pierret, M. Rosticher, T. Taniguchi, K. Watanabe, C. Maestre, C. Journet, B. Toury, V. Garnier, P. Steyer, J. H. Edgar, E. Janzen, J-M. Berroir, G. Fève, G. Ménard, B. Plaçais, C. Voisin, J-P. Hugonin, E. Bailly, B. Vest, J-J. Greffet, P. Bouchon, Y. De Wilde, E. Baudin
NATURE, in press, 2025. arXiv:2310.08351v5 [cond-mat.mes-hall]

[Yang_NATURE_NANOTECH2018] A graphene Zener–Klein transistor cooled by a hyperbolic substrate
W. Yang, S. Berthou, X. Lu, et al.
NATURE NANOTECHNOLOGY, v. 13, 47–52 (2018).

[Li_PHYS_REV_LETT2018] Near-Field and Far-Field Thermal Emission of an Individual Patch Nanoantenna
C. Li, V. Krachmalnicoff, P. Bouchon, J. Jaeck, N. Bardou, R. Haïdar, Y. De Wilde
PHYSICAL REVIEW LETTERS, v. 121, 243901 (2018).

[Abou_Hamdan_OPT_LETT2021] Hybrid modes in a single thermally excited asymmetric dimer antenna
L. Abou-Hamdan, C. Li, R. Haidar, V. Krachmalnicoff, P. Bouchon, Y. De Wilde
Optics Letters 46, 981-984 (2021). DOI: doi.org/10.1364/OL.413382

[Abou_Hamdan_ACS_PHOT2022] Transition from Phononic to Geometrical Mie Modes Measured in Single Subwavelength Polar Dielectric Spheres
L. Abou-Hamdan, L. Coudrat, S. Bidault, V. Krachmalnicoff, R. Haidar, P. Bouchon, Y. De Wilde
ACS Photonics 9, 7, 2295–2303 (2022). DOI: doi.org/10.1021/acsphotonics.2c00273

[Doumouro_PHYS_REV_APPL2021] Quantitative measurement of the thermal contact resistance between a glass microsphere and a plate
J. Doumouro, E. Perros, A. Dodu, N. Rahbany, D. Leprat, V. Krachmalnicoff, R. Carminati, W. Poirier, Y. De Wilde
PHYSICAL REVIEW APPLIED 15, 014063 (2021).

[De_Wilde_NATURE2006] Thermal Radiation Scanning Tunnelling Microscopy
Y. De Wilde, F. Formanek, R. Carminati, B. Gralak, P.-A. Lemoine, J.-P. Mulet, K. Joulain, Y. Chen, J.-J. Greffet,
NATURE 444, 740 (2006).

[Babuty_PHYS_REV_LETT2013] Blackbody spectrum revisited in the near-field
A. Babuty, K. Joulain, P.-O. Chapuis, J.-J. Greffet, Y. De Wilde
PHYSICAL REVIEW LETTERS, 110, 146103 (2013).

[Peragut_OPTICA2017] Hyperbolic metamaterials and surface plasmon polaritons
F. Peragut, L. Cerruti, A. Baranov,J.P. Hugonin, T. Taliercio, Y. De Wilde, J.J. Greffet
OPTICA, 4, 1409-1415 (2017).