Far-field nonlinear coherent optical nanoscopy of single emitters – FINDING
Coherent resonant nonlinear optical spectroscopy, such as four wave mixing, is a very powerful tool in nanosciences. It allows, to probe the electronic coherence, to manipulate the quantum states, and to explore the interactions between nano-systems and their environment. In addition, the level of investigation and manipulation of nanosystems increase with the reduction of the spatial area probed in an experiment. From biology to condensed matter physics, optical far-field microscopy is the most widely used tool for imaging and spectroscopy. Still the spatial resolution is limited by diffraction which leads to a limit around one micrometer for visible light. Stimulated emission depletion (STED) method has been developed to overcome this limit, it allows to reach lateral and axial resolutions typically between 20 and 70 nm.
The project relies on the development of a forefront experiment which merges these two approaches: coherent spectroscopy and super-resolved nanoscopy, in order to perform four wave mixing optical spectroscopy on single nanostructures with an unprecedented spatial resolution.
The coherent spectroscopy is based on optical heterodyning setup allowing to retrieve the nonlinear signals by spectral interferometry at the diffraction limit. The spatial submicrometric resolution will be reached with the development of a novel super-resolution scheme using doughnut-shape optical beam. However, unlike the STED, the method proposed here is derived from the suppression (or switching) of electronic coherences instead of the depletion of population.
This setup will be first tailored to study the coherent properties of single quantum dot (QD) structures emerging in two-dimensional materials such as transition metal dichalcogenides and hexagonal boron nitride monolayers. This forefront spectroscopy suits particularly to these new confined structures. The objective is twofold. Firstly, they presents the requested criteria, in term of optical coupling, to demonstrate the feasibility of the proposed super-resolution method. Conversely these QDs are very promising systems for quantum information processing. Indeed, they inherit exceptional properties from 2D materials, and they offer a strong potential for quantum behaviour and single photon emission at room temperature, which are keys elements for the development of quantum technologies.
The proposed spectroscopy will allow to explore their intrinsic quantum and dynamic properties which remain inaccessible with traditional spectroscopies limited by diffraction. In particular we will address the following questions:
i) What is the role of environment (chemical, electrostatic, mechanical) in decoherence processes of single QDs?And can it be optimised?
ii) How evolve the QD coherent properties as a function of temperature?
ii) Is that possible to address quantum couplings between single emitters?
iv) Finally, could we engineer decoherence and coupling in such structures in order to establish a novel platform for room temperature quantum processes?
Our original approach is general and could be then applied to a wide variety of systems. As a perspective in other condensed matter systems, it would open numerous appealing studies in dense samples of colloidal QDs and vacancy colour centres in diamond.
Beyond semiconductor physics such an experimental tool should stimulate, novel explorations in biophysics and bio-imaging. Recent evidences of electronic and vibrational coherences in chemical and biological systems suggests that quantum superposition can be robust against disorder and noise, and may enables new ways to enhance functional properties. Therefore the FWM nanoscopy could provide novel insights into the role of coherent processes in the photophysics of complex molecules..
Monsieur Francois Fras (Institut de physique et chimie des matériaux de Strasbourg)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IPCMS Institut de physique et chimie des matériaux de Strasbourg
Help of the ANR 241,065 euros
Beginning and duration of the scientific project: March 2019 - 36 Months