Raphaël Butté

raphael.butte@epfl.ch +41 21 693 33 57

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Nationality: French and Swiss

EPFL SB IPHYS LASPE
CH A3 465 (Bâtiment CH)
Station 6
1015 Lausanne

+41 21 693 33 57
Office: CH A3 465
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Expertise

Optical properties of semiconducting nanostructures with a focus on wide bandgap III-nitrides
Light-matter interaction in semiconductors
Physics of weakly interacting bosonic condensates
Polariton lasers
Photonic crystals
High-beta nanolasers
Physics of solid-state single photon emitters
Microring resonators and waveguides for nonlinear integrated photonic circuits

Expertise

Optical properties of semiconducting nanostructures with a focus on wide bandgap III-nitrides
Light-matter interaction in semiconductors
Physics of weakly interacting bosonic condensates
Polariton lasers
Photonic crystals
High-beta nanolasers
Physics of solid-state single photon emitters
Microring resonators and waveguides for nonlinear integrated photonic circuits

Mission

Explore the optical properties of III-nitride (III-N) semiconductors including low-dimensional heterostructures that can be integrated to nanophotonic platforms. His current research topics include but are not limited to:

The physics of waveguides operating in the strong exciton-photon coupling regime (polariton physics).
The properties of high-quality factor nanophotonic structures including microdisks and photonic crystals such as two-dimensional nanocavities and one-dimensional nanobeam cavities.
The investigation of the AlN-on-sapphire platform for realizing nonlinear photonic integrated circuits incl. waveguides and microring resonators.
Other research topics deal with the study of the optical properties of III-N nanostructures such as quantum wells and quantum dots and the investigation of the physical processes governing the internal quantum efficiency of III-N light emitters. A recent topic deals with the study of the photophysical properties of III-N solid-state single photon emitters.

Biography Publications Teaching & PhD

Raphaël Butté was born in Paris, France, in 1973. After receiving the PhD degree from the University Claude Bernard, Lyon, France, in 2000 for his research on the structural and optoelectronic properties of hydrogenated nanostructured silicon thin films with potential applications for photovoltaics and thin film transistors, he then moved to the University of Sheffield (2000-2003), UK, as a postdoctoral fellow in the group of Prof. Maurice S. Skolnick (Fellow of the Royal Society). There, his research shifted to the understanding of the optical properties of III-V semiconductors with a main focus on the nonlinear optical properties of cavity polaritons occurring in GaAs-based microcavities driven under resonant optical excitation.
In 2004, he moved to Ecole Polytechnique Fédérale de Lausanne (EPFL) as scientific collaborator in charge of optical spectroscopy at the Laboratory of Advanced Semiconductors for Photonics and Electronics (LASPE, https://www.epfl.ch/labs/laspe/), a newly established laboratory directed by Prof. Nicolas Grandjean. In 2010, he became permanent member of staff (Scientific Collaborator and Lecturer). He was promoted to the position of Senior Scientist in 2016.
His current research activity mostly deals with nanophotonics with a focus on the physics of planar waveguides, microring resonators, microdisks and photonic crystals made from III-nitride wide bandgap semiconductors.

He is the author of 129 scientific articles published in peer-reviewed international journals, 16 publications published in peer reviewed journals following an international conference (Web of Science > 5600 citations, h-index: 41; Google Scholar > 8000 citations, h-index: 48) and 6 book chapters.
He has given 32 invited talks in International Conferences/Winter-Summer Schools/Workshops.
He has been the co-chair of the European Semiconductor Laser Workshop 2022 (ESLW 2022). He has also been the Publications Chair/Guest Editor of the Proceedings of the 5th International Workshop on Nitride semiconductors (IWN2008) and also served as Scientific Secretary for IWN2008 and the 5th International Conference on Spontaneous Coherence in Excitonic Systems (ICSCE5).
In 2012, he was one of the 149 scientists recognized by the Outstanding Referee program (https://journals.aps.org/OutstandingReferees) of the American Physical Society (APS) selected from a pool of roughly 60,000 active referees. He has also received the Outstanding Reviewer Awards 2021 for the journal Applied Physics Express published by the Institute of Physics (IOP Publishing).
Since March 2024, he is an Associate Editor for the fully open access APS journal, Physical Review Research, for which he also acted as an Editorial Board Member since it was launched in September 2019 until securing this new editorial position.
Since August 2024, he is academic exchange advisor for the Physics section of EPFL.
Since November 2024, he is a council member (teaching body representative) of the faculty of basic sciences of EPFL.
From September 2013 until December 2017, he was one of the Editors of the journal "Superlattices and Microstructures" (Elsevier).
Since September 2015, he is a member of the Physics Doctoral School Teaching Committee of EPFL.
From September 2015 until August 2017, he was also a member of the EPFL Teaching Conference.
Member of the ANR (French research agency) committee CE57 «Physics of fundamental concepts and physics of dilute systems» for the call 2025 (AAPG 2025).

Main Scientific Achievements

Demonstration of the lowest midgap defect density for amorphous silicon related materials (Lyon)
Experimental investigation of the interplay between lower polariton relaxation rate and cavity photon lifetime for the formation of nonequilibrium polariton condensates (Sheffield)
First report of room temperature polariton lasing in bulk and quantum well based planar microcavities (EPFL)
First mapping of polariton condensation phase diagram over a temperature range spanning two orders of magnitude (EPFL),
Systematic study of the structural and optoelectronic properties of the InAlN alloy near lattice-matching to GaN (EPFL)
First systematic theoretical description of the emission properties of polariton laser diodes encompassing: the steady-state regime, the current modulation and the small-signal transient responses, the relative intensity noise, the turn-on delay and the emission linewidth (EPFL)
First report of cw blue lasing at room temperature in high-β III-nitride nanocavities grown on silicon incl. through quantum optical measurements (EPFL)
First demonstration of polariton lasing and nonlinear UV pulse modulation up to room temperature in polaritonic waveguides (EPFL)

Identification and thermal healing of focused ion beam-induced defects in GaN using off-axis electron holography

K. Ji; M. Schnedler; Q. Lan; F. Zheng; Y. Wang et al.

Applied Physics Express. 2024-01-01. DOI : 10.35848/1882-0786/ad163d.

Raphaël Butté

Expertise

Expertise

Mission

Main Scientific Achievements

Identification and thermal healing of focused ion beam-induced defects in GaN using off-axis electron holography

Optical and thermal characterization of a group-III nitride semiconductor membrane by microphotoluminescence spectroscopy and Raman thermometry

Investigation of the Impact of Point Defects in InGaN/GaN Quantum Wells with High Dislocation Densities

Polariton lasing in AlGaN microring with GaN/AlGaN quantum wells

Single photon emission and recombination dynamics in self-assembled GaN/AlN quantum dots

Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence

Ultrafast-nonlinear ultraviolet pulse modulation in an AlInGaN polariton waveguide operating up to room temperature

Dark-level trapping, lateral confinement, and built-in electric field contributions to the carrier dynamics in c-plane GaN/AlN quantum dots emitting in the UV range

Interplay of anomalous strain relaxation and minimization of polarization changes at nitride semiconductor heterointerfaces

Deep traps in InGaN/GaN single quantum well structures grown with and without InGaN underlayers

Interplay of intrinsic and extrinsic states in pinning and passivation of m-plane facets of GaN n-p-n junctions

Effects of 5 MeV electron irradiation on deep traps and electroluminescence from near-UV InGaN/GaN single quantum well light-emitting diodes with and without InAlN superlattice underlayer

Polariton relaxation and polariton nonlinearities in nonresonantly cw-pumped III-nitride slab waveguides

Toward Bright and Pure Single Photon Emitters at 300 K Based on GaN Quantum Dots on Silicon

Impact of defects on Auger recombination in c-plane InGaN/GaN single quantum well in the efficiency droop regime

III-nitride photonic cavities

Broadened Bandwidth Amplified Spontaneous Emission from Blue GaN-Based Short-Cavity Superluminescent Light-Emitting Diodes

Effects of InAlN underlayer on deep traps detected in near-UV InGaN/GaN single quantum well light-emitting diodes

Probing Alloy Formation Using Different Excitonic Species: The Particular Case of InGaN

Short cavity InGaN-based laser diodes with cavity length below 300 mu m

Probing alloy formation using different excitonic species: The particular case of InGaN

GaN surface as the source of non-radiative defects in InGaN/GaN quantum wells

Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations

Optical absorption and oxygen passivation of surface states in III-nitride photonic devices

Impact of surface morphology on the properties of light emission in InGaN epilayers

Excited states of neutral donor bound excitons in GaN

A quantum optical study of thresholdless lasing features in high-beta nitride nanobeam cavities

Impact of Mode-Hopping Noise on InGaN Edge Emitting Laser Relative Intensity Noise Properties

Burying non-radiative defects in InGaN underlayer to increase InGaN/GaN quantum well efficiency

Determining the nature of excitonic dephasing in high-quality GaN/AlGaN quantum wells through time-resolved and spectrally resolved four-wave mixing spectroscopy

Thin-Wall GaN/InAlN Multiple Quantum Well Tubes

Enhancement of Auger recombination induced by carrier localization in InGaN/GaN quantum wells

Quantification of scattering loss of III-nitride photonic crystal cavities in the blue spectral range

Propagating Polaritons in III-Nitride Slab Waveguides

Fermi-level pinning and intrinsic surface states of Al1-xInxNd(10(1)over-bar0) surfaces

Thresholdless Lasing of Nitride Nanobeam Cavities on Silicon

Carrier-density-dependent recombination dynamics of excitons and electron-hole plasma in m-plane InGaN/GaN quantum wells

Strain and compositional fluctuations in Al0.81In0.19N/GaN heterostructures

Statistical nanoscale study of localised radiative transitions in GaN/AlGaN quantum wells and AlGaN epitaxial layers

Fabrication defects and grating couplers in III-nitride photonic crystal nanobeam lasers (Conference Presentation)

Far-field coupling in nanobeam photonic crystal cavities

Optical properties of nearly lattice-matched GaN/(Al,In)N quantum wells

Small-signal transient response and turn-on delay of polariton laser diodes

Statistical correction of atom probe tomography data of semiconductor alloys combined with optical spectroscopy: The case of Al0.25Ga0.75N

Vectorial near-field imaging of a GaN based photonic crystal cavity

Continuous Wave Blue Lasing in III-Nitride Nanobeam Cavity on Silicon

Biexcitonic molecules survive excitons at the Mott transition

Gallium nitride L3 photonic crystal cavities with an average quality factor of 16 900 in the near infrared

Composition of Wide Bandgap Semiconductor Materials and Nanostructures Measured by Atom Probe Tomography and Its Dependence on the Surface Electric Field

Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

InGaN/GaN quantum wells for polariton laser diodes: Role of inhomogeneous broadening

M-Plane GaN/InAlN Multiple Quantum Wells in Core-Shell Wire Structure for UV Emission

Q-factor of (In,Ga)N containing III-nitride microcavity grown by multiple deposition techniques

Impact of saturation on the polariton renormalization in III-nitride based planar microcavities

Relative intensity noise and emission linewidth of polariton laser diodes

Optical, structural, and morphological characterisation of epitaxial ZnO films grown by pulsed-laser deposition

Large-k exciton dynamics in GaN epilayers: Nonthermal and thermal regimes

Intrinsic degradation mechanism of nearly lattice-matched InAlN layers grown on GaN substrates

Investigation of InGaN/GaN quantum wells for polariton laser diodes

Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

High quality factor two dimensional GaN photonic crystal cavity membranes grown on silicon substrate

LIGHT-EMITTING DIODES Solid-state lighting on glass

A novel class of coherent light emitters: polariton lasers

Strain compensation in AlInN/GaN multilayers on GaN substrates: Application to the realization of defect-free Bragg reflectors

Tailoring the light-matter coupling in anisotropic microcavities: Redistribution of oscillator strength in strained m-plane GaN/AlGaN quantum wells

Polariton lasing in a hybrid bulk ZnO microcavity

Probing exciton density of states through phonon-assisted emission in GaN epilayers: A and B exciton contributions

Spin relaxation of free excitons in narrow GaN/AlxGa1-xN quantum wells

POLARIZATION BEHAVIOR ABOVE THE POLARITON CONDENSATION THRESHOLD IN A GaN-BASED MULTIPLE QUANTUM WELL MICROCAVITY

PHASE DIAGRAM OF EXCITON-POLARITONS IN MULTIPLE QUANTUM WELL GaN-BASED MICROCAVITIES

Condensation phase diagram of cavity polaritons in GaN-based microcavities: Experiment and theory

Pinning and Depinning of the Polarization of Exciton-Polariton Condensates at Room Temperature

Anomalous composition dependence of the band gap pressure coefficients in In-containing nitride semiconductors

GaN-based embedded 2D photonic crystal LEDs: Numerical optimization and device characterization

Room temperature polariton lasing in III-nitride microcavities, a comparison with blue GaN-based vertical cavity surface emitting lasers