Stefan DILHAIRE is member of Photonique & Matériaux team, his research field is Ultra Fast & Nano Scale Energy Transfer

Stefan Dilhaire’s group studies mutual interaction of heat, light and electricity in microsystems and nanomaterials and its applications in renewable energy (thermoelectricity, thermionicity, Organic photo generation), in microelectronics, in nanoplasmonics, in biology (ultrasonic imaging of cells).

The group is currently involved in 3 actions:

  • Nanoscale ultrafast energy transport (Nano thermal physics, Picosecond ultrasonics, Thermal properties identification),
  • Imaging (Integrated circuits temperature mapping),
  • Technology Transfer (Development of new optical techniques such as Heterodyne optical sampling aka ASOPS)

The research field concerns the study of mechanisms of transport of energy in nano-materials. These mechanisms can be achieved by phonons, plasmons, phonons polaritons. Materials consist in nano-particles, of nanowires, super-lattices or nanometric layers. The challenges are of:

  • working and characterising energy transport of matter at the nanoscale
  • uncorrelate the electric properties from the thermal properties.

Applications have repercussions in the fields of renewable energies (thermoelectricity), microelectronics as well as biology (laser ultrasound imaging of live cells)

Innovative imaging

Two Experimental Approaches

  1. Scanning thermal microscopy (SThM) : This method is an AFM based technique where the tip is instrumented with a temperature sensitive apex able to heat and probe at the same time. Scanning the tip produces images contrasted by the thermal conductivity of the sample with a nanometric lateral resolution. SThM was successfully applied to the characterization of thermal transport in nanowires.
  1. Femtosecond pump-probe Imaging :Femtosecond transient thermoreflectance is used for measuring temperature changes at a surface with high temporal resolution (100fs). It employs as a probe the thermally induced change in the optical constants of the metal by measuring the intensity of a light beam being reflected at the surface under consideration. However, since the optical constants are not very sensitive to the temperature, signals obtained are usually small, and enhancement of the sensitivity of the method is desirable. For that, we use an ultra fast heterodyne pump-probe spectroscopy.  This patented dual laser method achieves pump-probe delay times without a linear translation stage, but by using the beat frequency of two slightly detuned cavity-length-locked lasers instead.  The lack of a physical delay stage removes artifacts relating to alignment and beam walking.  The total pump-probe delay time, equal to the repetition period of the pump laser (~10s of ns) is collected in the beat period between the two lasers, ~10s of ms, and is ideal for high resolution microscopy.

Research Fields

Research Fields

  1. Ultrafast Energy Transfer at the nanoscale: Nanoplasmonics

Light propagating in concert with electrons along a metal surface may one day be used to turn microchips into optical processors. We showed that the loss of energy suffered by such metal-skimming light waves can be reduced if the waves are produced at a nanoscale slit in the metal film that carries the waves. The measurements are the first to provide a direct probe of the light losses in the vicinity of a subwavelength aperture. This effect is the result of interference between two different kinds of waves generated by the slit.

Weused a 300-nanometer-wide slit in a gold film deposited on a glass substrate. The film was illuminated from below with an infrared (800 nanometer) laser pulse, producingSPPs on the top surface, propagating outward, perpendicular to the slit direction. As the waves died out and were absorbed by the metal, they heated it enough to affect the surface’sability to reflect light. The SPP absorption wasprobed by firing a second, time-delayed laser (532 nanometers) at many locations on the top of the film and detected the reflected light. These so-called thermoreflectance data showed a plateau between 5 and 15 micrometers from the slit, which meant that the absorption was constant over this region.

  1. Ultrafast Energy Transfer at the nanoscale: Nanophononics

The ability to precisely control the thermal conductivity (k) of a material is fundamental in the development of on-chip heat management or energy conversion applications. Nanostructuring permits a marked reduction of k of single-crystalline materials, as recently demonstrated for silicon nanowires. However, silicon-based nanostructured materials with extremely low k are not limited to nanowires. By engineering a set of individual phonon-scattering nanodot barriers we have accurately tailored the thermal conductivity of a single-crystalline SiGe material in spatially defined regions as short as ∼15 nm. Single-barrier thermal resistances between 2 and 4×10−9 m2 K W−1 were attained, resulting in a room-temperature k down to about 0.9 W m−1 K−1, in multilayered structures with as little as five barriers. Such low thermal conductivity is compatible with a totally diffuse mismatch model for the barriers, and it is well below the amorphous limit. The results are in agreement with atomistic Green’s function simulations.… tobecontinuedin…Precise control of thermal conductivityat the nanoscalethroughindividual phonon-scatteringbarriers (Nature Materials 9, 491–495 (2010))

  1. Advanced Imaging: Filming a temperature field at 10 Tera Images per second

The problem for the experimenter is how to measure electron temperature, Te, resulting from optical absorption. Non-contact techniques like optical reflection are ideal but require knowledge about the variation of reflectivity with Te. In noble metals, the reflectivity can be successfully utilized for this purpose.The relative change in reflectivity has a large magnitude and ∆R/Rscales almost linearly with electron temperature. A linear relationship between ∆R/R and Teopens the way for a simple analysis of measured transient reflectivities.LOMA is specialized in thermal imaging and ultra-fast heat transfer analysis. Our expertise in the area of Heterodyne Time Domain Thermoreflectance (HTDTR) is at the state of the art.We have demonstrated that pump-probe experiments are of great use to measure thermal properties on thin films and nano-structured materials. The use of ultra-short laser pulses (100 fs) in pump-probe experiments allows characterizing thermal properties of nano-objetcs. LOMA has developed an unique expertise in heterodyned femto-second sources rendering temporal sampling purely optical thus dividing the acquisition time by 3 orders of magnitude.

  1. Advanced imaging: Thermal transport in individual nanowires

Thermal imaging of individual silicon nanowires (Si NWs) is carried out by a scanning thermal microscopy (SThM) technique. The vertically aligned Si NWs are fabricated combining nanosphere lithography and metal-induced wet chemical etching. A thermal model for the SThM probe is implementedfor the probe calibration, and to extract thermal parameters from the sample under study. Using this model combined with the experimental thermal images, we determine a mean value of the tip-to-sample thermal contact resistance and a mean value of the Si NWs thermal conductivity. SThM is actually the only technique available to perform thermal measurements simultaneously on an assembly of individual one-dimensional nanostructures. It enables a statistical process of thermal data in order to deduce a reliable mean thermal conductivity.

  1. Industrial applications 

Pump-probe experiments are of great use to measure thermal properties on thin films and nano-structured materials. The use of ultra-short laser pulses (100 fs) in pump-probe experiments allows characterizing thermal properties of thin films. However, access to long pump-probe delay times (10’s of nanoseconds) in a reliable way with a reasonable time measurement (few minutes) remains impossible in classical pump-probe experiments, as they are limited by physical modulation of laser path length. LOMA has developed an unique expertise in heterodyned femto-second sources rendering temporal sampling purely optical thus dividing the acquisition time by 3 orders of magnitude. Thermal conductivity screening on a substrate containing an array of samples with different thermal conductivities is now accessible in routine. Filming the thermal response to a light flash of a whole surface allows to map the thermal properties at once, thereby considerably reducing the acquisition time.

The group has developed a unique expertise at the state of the art in heterodyned femto-second sources rendering temporal sampling purely optical thus lowering the acquisition time by 3 orders of magnitude in comparison to classical techniques. We are currently doing researche and development with different laser companies.



A. Shakouri (UC Santa Cruz, University of Purdue USA), T. Baba (Tsukuba Japan), J. Altet (UPC, Spain), S. Volz (ECP Paris), N. Mingo (CEA Grenoble), G. Tessier (ESPCI Paris), B. Audoin (I2M Bdx), J.C Batsale (I2M Bdx), S. Ravaine (CRPP Bdx), G. Hadzianou (LCPO, Bdx), Philippe Lalanne, (IOGS-LP2N Bdx), Pierre-Michel Adam UTT (Troyes), Guillaume Duchateau, (CELIA-CEA Bdx).


My publications in Hal Archive


  1. A. Ben Amor, D. Djomani, M. Fakhfakh, S. Dilhaire, L. Vincent and S. Grauby, Si and Ge allotrope heterostructured nanowires: experimental evaluation of the thermal conductivity reduction, Nanotechnology, Volume 30, Number 37, (2019).
  2. Lalanne, P., Coudert, S., Duchateau, G., Dilhaire, S., Vynck, K. Structural Slow Waves: Parallels between Photonic Crystals and Plasmonic Waveguides, ACS Photonics, 6 (1), (2019)
  3. Petsagkourakis, I., Pavlopoulou, E., Cloutet, E., Chen, Y.F., Liu, X., Fahlman, M., Berggren, M., Crispin, X., Dilhaire, S., Fleury, G., Hadziioannou, G, Correlating the Seebeck coefficient of thermoelectric polymer thin films to their charge transport mechanism, Organic Electronics: physics, materials, applications, 52, pp. 335-341, (2018).
  4. Lozan, O., Sundararaman, R., Ea-Kim, B., Rampnoux, J.-M., Narang, P., Dilhaire, S., Lalanne, P., Increased rise time of electron temperature during adiabatic plasmon focusing, Nature Communications, 8 (1), art. no. 1656, . (2017)
  5. Coffy, E., Dodane, G., Euphrasie, S., Mosset, A., Vairac, P., Martin, N., Baida, H., Rampnoux, J.M., Dilhaire, S., Anisotropic propagation imaging of elastic waves in oriented columnar thin films,  Journal of Physics D: Applied Physics, 50 (48), art. no. 484005, . (2017)
  6. D’Acremont, Q., Pernot, G., Rampnoux, J.-M., Furlan, A., Lacroix, D., Ludwig, A., Dilhaire, S., High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library, Review of Scientific Instruments, 88 (7), art. no. 074902, (2017)
  7. Furlan, A., Grochla, D., D’Acremont, Q., Pernot, G., Dilhaire, S., Ludwig, A., Influence of Substrate Temperature and Film Thickness on Thermal, Electrical, and Structural Properties of HPPMS and DC Magnetron Sputtered Ge Thin Films, Advanced Engineering Materials, 19 (5), art. no. 1600854, .(2017)
  8. Petsagkourakis, I., Pavlopoulou, E., Portale, G., Kuropatwa, B.A., Dilhaire, S., Fleury, G., Hadziioannou, G., Structurally-driven enhancement of thermoelectric properties within poly(3,4-ethylenedioxythiophene) thin films, Scientific Reports, 6, art. no. 30501, (2016)
  9. Michaud, J., Béchou, L., Veyrié, D., Laruelle, F., Dilhaire, S., Grauby, S., Thermal Behavior of High Power GaAs-Based Laser Diodes in Vacuum Environment, IEEE Photonics Technology Letters, 28 (6), art. no. 7347350, pp. 665-668. (2016)
  10. Casanova, A., D’Acremont, Q., Santarelli, G., Dilhaire, S., Courjaud, A., Ultrafast amplifier additive timing jitter characterization and contro, lOptics Letters, 41 (5), pp. 898-900. (2016)
  11. Chandezon, J., Rampnoux, J.-M., Dilhaire, S., Audoin, B., Guillet, Y. In-line femtosecond common-path interferometer in reflection mode (2015) Optics Express, 23 (21), pp. 27011-27019
  12. Savelli, G., Silveira Stein, S., Bernard-Granger, G., Faucherand, P., Montés, L., Dilhaire, S., Pernot, G. Titanium-based silicide quantum dot superlattices for thermoelectrics applications (2015) Nanotechnology, 26 (27), art. no. 275605
  13. Dehoux, T., Ghanem, M.A., Zouani, O.F., Rampnoux, J.-M., Guillet, Y., Dilhaire, S., Durrieu, M.-C., Audoin, B. All-optical broadband ultrasonography of single cells (2015) Scientific Reports, 5, art. no. 8650
  14. Rojo, M.M., Martín, J., Grauby, S., Borca-Tasciuc, T., Dilhaire, S., Martin-Gonzalez, M. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: New approaches towards thermal transport engineering of organic materials (2014) Nanoscale, 6 (14), pp. 7858-7865 .
  15. O. Lozan, M. Perrin, B. Ea-Kim, J. M. Rampnoux, S. Dilhaire, and P. Lalanne, Anomalous Light Absorption around Subwavelength Apertures in Metal Films, Phys. Rev. Lett. 112, 193903 (2014)
  16. A. Abbas, Y. Guillet, J.-M. Rampnoux, P. Rigail, E. Mottay, B. Audoin, and S. Dilhaire, Picosecond time resolved opto-acoustic imaging with 48 MHz frequency resolution, Optics Express, Vol. 22, Issue 7, pp. 7831-7843 (2014)
  17. M. Muñoz Rojo, S. Grauby, J.-M. Rampnoux, O. Caballero-Calero, M. Martin-Gonzalez and S. Dilhaire, Fabrication of Bi2Te3 nanowire arrays and thermal conductivity measurement by 3ω-scanning thermal microscopy, J. Appl. Phys. 113, 054308 (2013)
  18. Karim Aissou, Jonah Shaver, Guillaume Fleury, Gilles Pécastaings, Cyril Brochon, Christophe Navarro, Stéphane Grauby, Jean-Michel Rampnoux, Stefan Dilhaire and Georges Hadziioannou, Nanoscale Block Copolymer Ordering Induced by Visible Interferometric Micropatterning: A Route towards Large Scale Block Copolymer 2D Crystals, Adv. Mater. 25, 213–217 (2013)
  19. S. Dilhaire, G. Pernot, G. Calbris, J. M. Rampnoux, and S. Grauby, Heterodyne picosecond thermoreflectance applied to nanoscale thermal metrology, J. Appl. Phys. 110, 114314 (2011)
  20. Altet, J., Mateo, D., Perpiñà, X., Grauby, S., Dilhaire, S., Jordà, X., Nonlinearity characterization of temperature sensing systems for integrated circuit testing by intermodulation products monitoring, Review of Scientific Instruments 82 (9) , art. no. 094902, 2011
  21. Pradere, C., Clerjaud, L., Batsale, J.C., Dilhaire, S., High speed heterodyne infrared thermography applied to thermal diffusivity identification, Review of Scientific Instruments 82 (5) , art. no. 054901, 2011
  22. Etienne Puyoo, Stéphane Grauby, Jean-Michel Rampnoux, Emmanuelle Rouvière, and Stefan Dilhaire,  Scanning thermal microscopy of individual silicon nanowires, J. Appl. Phys. 109, 024302 (2011)  
  23. Thermal exchange radius measurement: Application to nanowire thermal imaging, Puyoo, E., Grauby, S., Rampnoux, J.-M., Rouviere, E., Dilhaire, S. , Review of Scientific Instruments 81 (7), art. no. 073701  (2010)
  24. Aldrete-Vidrio, E., Mateo, D., Altet, J., Salhi, M. A., Grauby, S., Dilhaire, S . Strategies for built-in characterization testing and performance monitoring of analog RF circuits with temperature measurements. Measurement Science and Technology, 21(7)  (2010)
  25. Heterodyne method with an infrared camera for the thermal diffusivity estimation with periodic local heating in a large range of frequencies (25 Hz to upper than 1 kHz), Lilian Clerjaud, Christophe Pradere, Jean-Christophe Batsale and Stefan Dilhaire, Quantitative InfraRed Thermography Journal Volume 7, Issue 1, 2010
  26. G. Pernot, M. Stoffel, I. Savic, A. Jacquot, J. Schumann, G. Savelli, A. Rastelli, O.G. Schmidt, J. M. Rampnoux, S. Dilhaire, M. Plissonnier, S. Wang, and N. Mingo, “Precise control of thermal conductivity at the nanoscale via individual phonon barriers”, Nature Materials, Volume : 9, Pages : 491–495 (2010)

Book Chapters

  1. Handbook of Semiconductor Nanostructures and Nanodevices, Edited by A. A. Balandin and K. L. Wang, USA, ISBN: 1-58883-073-X, Chapter 29 « Scanning Thermal MicroscopyApplied to Thin films and ElectronicDevicesCharacterization », S. Volz, S. Dilhaire, S. Lefebvre, L.D.Patino-Lopez.
  2. Micro et Nano thermique manuscrit, éditions du CNRS, ISBN 978-2-271-06462-2 Chapitre 10 : Méthodes optiques, Stefan Dilhaire, Danièle Fournier, Gilles Tessier
  3. Microscale and nanoscaleheattransfer / SebastianVolz (ed.) ; in collaboration with Rémi Carminati, Patrice Chantrenne, Stefan Dilhaire, Séverine Gomez, Nathalie Trannoy, Gilles Tessier., Ed Springer, ISBN : 978-3-540-3605-6


– Surface preparation method
Publication number: 20150140267
Abstract: The invention relates to a process for the preparation, by spatial distribution of light intensity, of a surface in relief promoting order and spatial coherence serving as a guide for the organization, on nano- and micrometre scales, of an overlayer on the surface in particular of block copolymers.

– Optical Heterodyne Sampling Device
Publication number: 20080251740
Abstract: An optical heterodyne sampling device includes: two pulsed laser sources which may have a jitter and which can receive respectively a pump beam and a probe beam having respective repetition frequencies Fs and Fp; and an element for combining the pump beam and the probe beam which are intended to be passed over a sample, consisting of a signal channel including a system for the photodetection of the response signal from the sample and a system for acquiring the photodetected signal, which is connected to the signal channel. According to the invention, Fs and Fp are essentially constant and the acquisition system includes an acquisition trigger element. A synchronization channel is connected to the trigger element, and includes a device for measuring the beat frequency |Fs-Fp| which can generate a synchronization signal comprising pulses each time the pulses of the pump beam and the probe beam coincide.

Curriculum vitae

Curriculum vitae


Head of the Ultra Fast and Nanoscale Energy Transfer  aka TIPI research group at LOMA


Université Paris X                  Electrical Engineering                         B. Tech, 1988

Université Bordeaux 1        Electrical Engineering                         M.S., 1990

Electrical & Optical Engineering     PhD, 1994

HDR 2001.


Professor, University of Bordeaux                                                    Dec 08 to present


PhD offers

 PhD title


Scanning near field Thermo Optical Microscopy (STOM) of ultrafast hotspots

Femtosecond optics, Near field microscopy, Plasmonics, Nanoscale heat transfer.

Research project

(36 months)

Context:Thermal properties are critical to performances of devices in many applications, especially at the nanoscale. The main challenges associated with designing and optimizing thermal transport and energy conversion at the nanoscale are related to (i) Understanding and providing a description of heat carrier generation, (ii) understanding heat transport mechanisms at the nanoscale and improving thermal management methods to enhance device performances or reliability and (iii) controlling heat flow at the nanoscale by means of passive or active elements, as well as its conversion into other forms of energy.

Despite very significant theoretical and experimental efforts in these fields, important technical challenges remain to be solved. Indeed, thermal transport at the nanoscale does not follow standard diffusion mechanisms, unlike what occurs at the micro- and macro-scales. At these scales, the empirical Fourier law, which states that thermal conductivity is independent of sample length, provides an accurate description of thermal transport. At the nanoscale however, this law is not valid anymore and the actual heat transport mechanisms remain to be confirmed. To experimentally investigate these mechanisms, it is of critical importance to access to nanometer scales but also time-scales corresponding to transport along such distances, typically well below the nanosecond and down to sub-picosecond scales.

Objectives: This PhD has two main objectives. First, optical techniques will be used to simultaneously achieve the required spatial and temporal resolution to investigate heat and energy transport at the nanoscale. This aspect comprises the creation of a nanoscale heat source and building the system to measure the thermal relaxation. The second objective is to experimentally highlight transport mechanisms that deviate from the empirical Fourier law. Practically, the candidate will complete the development of the characterization system that is based on an optical near-field method coupled to a pump probe thermal measurement technique. The candidate will also characterize a variety of samples provided by partners to demonstrate non-Fourier heat transport and propose thermal management and energy conversion strategies for nanodevices.

Approach: The candidate will use optical techniques to achieve the objectives of the project. Indeed, light is ideal for both hotspots creation and contactless measurements of the thermal properties. Metallic nanostructures will be used to convert incoming light into plasmons, which will be focalized into sub-wavelength areas, well below the diffraction limit. Likewise, temporal dynamics occurring in several dozens of femtoseconds are accessible thanks to the relativistic speed of plasmons propagation. This technique will be used to achieve ultimate temporal and spatial confinement of the heat source.

To measure the dynamics with similar spatial and temporal resolutions, the candidate will contribute to the development of a system combining a near-field optical microscope and a pump-probe thermoreflectance system with femtosecond light pulses. To the best of our knowledge, this technique has never been reported before in the literature and will prove invaluable to demonstrate non-diffusive heat and energy transport mechanisms. The candidate will also implement the nanohotspot device in this measurement system.

The second step will consist in using this system to perform time-resolved measurements with sub-100 nm spatial resolution. The candidate will contribute to the choice of samples and materials needed to observe non-diffusive thermal transport and characterize them.

Details of the position :

Academic background: Master degree or equivalent in physics, engineering, optics or related fields

Required knowledge and skills: Optics and optical systems, ultrafast spectroscopy, micro and nano heat transfer. Additional required skills:

  • Practical experience with softwares such as Matlab and Labview.
  • Business level English required.
  • Hands-on laboratory experience.

What we expect: The candidate should be active and rigorous, curious and eager to perform experimental work. He should also have good communication skills and enjoy working in a collaborative environment. He will attend regular group meetings and is expected to disseminate his results in conferences as well as through written publications.

Our offer to you: You will be hosted in the Ultrafast and Nanoscale energy transport group in LOMA, an institute located on the campus of the University of Bordeaux. You will work alongside other PhD students and several permanent researchers with proven expertise in the field. The campus is 15 minutes away from the center of the city of Bordeaux which is listed as a “Word Heritage Site” by UNESCO. You will be under a CNRS work contract with competitive salary and included health insurance.

Application procedure: The application should be written in French or English and sent electronically as a single PDF file containing the following documents:

CV including:

–  Complete list of publications,

–  Two references that we can contact.

Cover letter, 2 pages maximum where you describe:

–  Yourself and present your qualifications,

–  Why you are interested and motivated by this specific position

–  Your future goals and research focus.

Contact: Stefan Dilhaire:, 05 40 00 27 86

Starting date: 04/10/2021

Name of the Post-Doc advisor(s) Stefan Dilhaire:, 05 40 00 27 86
Group Ultra Fast and NanoScale Energy Transport
List of the partners (lab/company/univ.) CNRS, Université Paris Sud, Paris-Saclay.
Post-Doc title

Research project

Name of the PhD advisor(s)

(E-mail, Tel)

Stefan Dilhaire,

Jeremie Maire,

Group Ultra Fast and NanoScale Energy Transport
List of the partners (lab/company/univ.) I2M


Laboratoire Ondes et Matière d’Aquitaine
351 cours de la libération
33405 Talence Cedex

Phone : + 33 (0)5 40 00 27 86

Auteur / autrice