The "Nano-Optics" group is interested in the optical properties of nano-objects, which can be either semiconductor based heterostructures or less classical materials like carbon nanotubes, nanodiamonds or transition metal dichalcogenide-based bidimentional structures. These nano-objects can be considered as the building blocks necessary to the implementation of a quantum treatment of the information in solid state physics. We are particularly involved in the development of new integrated non classical light sources (Optical Parametric Oscillators, twin photons and single photon sources) and in the conception of new devices based on quantum optics effects.
- Single carbon nanotube spectroscopy
The geometrical structure of a carbon nanotube is very simple: a graphene sheet is enrolled to form a tube with typical length 1 µm. The tube diameter is about one nanometer. This kind of quasi-onedimensional nano-object shows numerous unique mechanical or electronic propertiesnales.
The study of carbon nanotubes optical properties (apart from Raman) really started after the publication in 2002 of a paper by the Rice University group reporting on the observation of photoluminescence signal at room temperature arising from aqueous suspensions of nanotubes. In fact carbon nanotubes self organize in bundles and have to be isolated for light emission. We have developped optical techniques of investigation and shown how to address a specific class of carbon nanotubes within an ensemble by combining selective optical excitation and appropriate detection. By time-resolved measurements we have also demonstrated the key role played by nanotube-nanotube and nanotube-environment interactions in the light emission process. Moreover low temperature measurements allowed to obtain important results on the excitonic structure of these nano-objects.
Up to now all measurements were performed on large ensembles of nanotubes and our current interst deals with single nanotube spectroscopy.
(For more informations see the section "Carbone Nanotubes")
- Quantum optics with NV centers
We are exploiting the possibility to have lifetime limited emitters in diamond to observe quantum electro-dynamical effects in the solid state.
Light from a single NV center in a diamond will be be retroreflected by a distant mirror to change its spontaneous emission lifetime.
We will also realize an experiment where a single atom will be playing the role of a mirror in a half cavity.
NV centers or other coloured centers, such as the SIV center, are very well suited for these experiments.
We are also investigating levitating nanodiamonds for hybrid opto-mechanics.
(More informations are available in section : "Colored centers in Diamond for quantum optics".)
- Pattern formation in multiple microcavities
The specificity of semiconductor microcavities resides in the existence of a strong light-matter coupling, which gives rise to mixed states, the polaritons. We mainly focused our attention on the parametric scattering processes which take place in these systems. Indeed, Optical Parametric Oscillations give rise to intriguing properties such as the spontaneous self-organization of light in patterns. Understanding the basic mechanisms
at stake allows for the engineering and the realization of non-linear optical functions such as optical switches.
(More informations are available in the section "semiconductor microcavities" .)
- Van der Waals heterostructures
During the last decade, research on graphene has brought considerable breakthroughs in a number of domains ranging from high-speed electronics to metrology. However, graphene is a zero-bandgap semiconductor and a graphene layer on its own is not appropriate for applications in optoelectronics or as nano-emitter for nanophotonics. Different routes are explored to obtain semiconducting graphene-like structures. The most famous is the development of transition metal dichalcogenides (TMD), which are layered materials that share their structure with graphene and present direct optical bandgaps of a few electronvolt for monolayers, leading to a strong excitonic photoluminescence from the near infrared to the visible. The spin control of the excited states through the polarization of the excitation beam opens the way to optospintronics, and the development of heterostructures, combining TMDs monolayers with graphene and/or boron-nitride, should also allow building original optoelectronic devices.
(More informations are available in the section "Van der Waals heterostructures" .)
- Ultra-coherent single photon source with InAs/GaAs quantum dots.
Single semiconductor QDs, which are considered as two-level systems in the artificial atom model, are promising structures for the realization of integrated devices such as single photon sources for quantum information applications. However, contrary to genuine atoms, they are condensed matter systems which suffer from the coupling to their solid environment, leading to a degradation of the coherence of the emitted photons. By using an original experimental setup that spatially decouples the excitation and detection paths we were able to perform strictly resonant excitation of a quantum dot at low temperature nearly reaching the radiative limit where T2 = 2T1 and explore the resonant Rayleigh scattering (RRS) regime where QDs emit single photons with the laser coherence time. The resulting "ultra-coherent" single photon source opens the way for integrated quantum devices where the generation of indistinguishable single photons is tailored by the excitation laser source.
(for more informations see the section "Quantum dots")