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)

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

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 126 scientific articles published in peer-reviewed international journals, 14 publications published in peer reviewed journals following an international conference (Web of Science > 5400 citations, h-index: 40; Google Scholar > 7600 citations, h-index: 46) 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.