BOÎTES QUANTIQUES ET NANOSTRUCTURES PHOTONIQUES (QD)
Responsable : Sébastien SAUVAGE
Centre de Nanosciences et de Nanotechnologies
Large part of the activity of the group focuses on photonic crystals which are designed, modeled, measured and fabricated by the team in the clean room facility of the Centre. We study in particular the enhancement of non-linear interactions in photonic crystal nanocavities made of silicon, diamond, germanium or nitride materials: Second harmonic generation, frequency tripling, Raman emission, auto-oscillations, two-photon absorption photodetection, biosensing etc. We also investigate light emission in tensile strained germanium to provide efficient optical sources for silicon photonics. The historical part of the activity is dedicated to the local control of photonic energy and the enhancement of the interaction between light (photons) and matter (electrons, phonons) at the smallest nanometric scales. We like looking at semiconductor nanostructures with strong electronic confinement like semiconductor self-assembled quantum dots. Self-assembled quantum dots are semiconductor nanostructures with characteristic dimensions in the nanometer or tens of nanometers scale. Self-assembled quantum dots can be formed spontaneously by growing lattice mismatched materials like InAs on GaAs or Ge on Si. The physics and the potential applications of these nanostructures are incredibly rich. At the nanometer length scale, the motion of the carriers is governed by quantum mechanics and the energy levels are quantized just like atoms or molecules. From this point of view [of discrete energy levels], self-assembled quantum dots can be considered as artificial atoms inserted into a solid matrix. However this picture is limited. The coupling of the carriers with the environment like the vibration modes of the crystals, leads to very specific properties and interaction mechanisms. We account for the electron-phonon interaction in semiconductor quantum dots which leads to the formation of polarons (entangled electron-phonon quasiparticule), in particular in the far infrared spectral range: time-resolved relaxation and decoherence dynamics, non-linearity like second and third harmonic generation, multiband k.p modelling of the electronic structure and infrared spectroscopy going from ensemble to single quantum dot measurements corresponding to a sub-wavelength ultrasensitive absorption nanospectroscopy instrumentation.
Semiconductor quantum dots are potential candidates for several type of optoelectronic devices like long wavelength lasers or midinfrared photodetectors with improved performances as compared to bulk or two-dimensional heterostructures. They are also potential candidates for quantum information processing as single photon sources or support of qubits. Our group studies different materials in particular those related to InAs/GaAs quantum dots and Ge/Si self-assembled quantum dots.