Research topics

The motion of a mesoscopic mechanical resonator, made up of a large number of atoms, can exhibit quantum behavior when cooled. Such a regime is accessible at cryogenic temperatures close to absolute zero, in the millikelvin range, and for resonators with frequencies in the gigahertz range. Coupling such mechanical objects to light then provides a means of manipulating their quantum vibrations: phonons, the energy quanta associated with mechanical motion, can be measured, added or removed one by one, interacting with photons that can be detected individually.

This ultimate control of quantum motion is expected to play an important role in applications for high-sensitivity detection of physical signals, in the development of quantum information technologies, or in fundamental tests of quantum mechanics on objects of intermediate mass, on the order of the Planck mass.

Optomechanical disk resonator sitting on a planar phononic shield that minimizes anchoring losses.

To explore these questions, our team has developed special nano-optomechanical resonators, where the coupling between light and vibration, as well as the dissipation mechanisms (optical and mechanical), have been optimized. Our experiments involve operating these systems in a dilution cryostat, where original nano-photonics instrumentation has been developed, combining nano-positioning, confocal microscopy and single-photon quantum optics techniques.

List of our key publications on the subject :

. Physical Review Letters 105 (26), 263903 (2010)

. Optics Express 22 (12), 14072-14086 (2014)

. Optica 4 (2), 218-221 (2017)

. Physical Review Letters 120 (22), 223601 (2018)

. Physical Review Letters 124 (8), 083601 (2020)

. Physical Review A 101, 063820 (2020)

The interaction between optomechanics and liquids is a complex subject, mixing hydrodynamics, electromagnetism and elasticity theory.

Liquids are themselves complex physical systems: they are made up of a very large number of interacting molecules. While it is virtually impossible to follow the trajectory of an individual molecule in a liquid, the molecules collectively adopt regular behaviors, which are described by the Navier and Stokes equations. These equations provide a very good approximation of liquids on a macroscopic scale. On the other hand, at small spatial scales and short timescales, the limit of validity of these equations is in question.

When used as physical probes, optomechanical systems offer exceptional sensitivity and temporal resolution. In recent years, our team has also demonstrated that they are compatible with operation in a liquid medium, whether completely immersed in the liquid, or interacting with a small volume of it. Optomechanical systems therefore appear to be prime candidates for testing the limits of validity of the hydrodynamic equations, but also for probing phenomena predicted by these equations on nanoscopic scales and at the shortest times. A new generation of sensors based on the principles of optomechanics is emerging in liquid media, with implications for nanoscale wetting physics, biodetection technologies and the imaging of microscopic processes in living organisms. Our team works on both upstream and downstream aspects of these topics.

Optomechanical disk resonator interacting with a liquid.

. Nature Nanotechnology 10 (9), 810-816 (2015)

. Nature Communications 13 (1), 6462 (2022)

. Physics of Fluids 35 (5) (2023)

Optomechanics involves the interaction of light and mechanical vibrations. Polaritonics involves the interaction of light and electronic excitations. Optomechanics and polaritons therefore ultimately combine light and two distinct forms of excitation of matter. These three entities can interact with each other, particularly in semiconductors, where heterostructures can be finely designed to control and optimize interactions.

Our research into polaritonic optomechanics has enabled us to modify the canonical image of optomechanics, by replacing photons with polaritons, producing situations of enhanced coupling between light and vibrations. This modification is also accompanied by a large increase in physical non-linearities, offering new opportunities for controlling quantum states of motion and for spatio-temporal patterning of vibrations and light.

Finally, optomechanics enables us to probe the physics of polaritons mechanically, opening up a new tool for study in the field of polaritonics.

Polaritonic optomechanical resonator. (a) An optomechanical disk incorporates a collection of five quantum wells. (b) This hybrid resonator combines three degrees of freedom: optical, mechanical and electronic. (c) It can be made from the Arsenide, Gallium, Aluminium and Indium family of materials.

List of our key publications on the subject:

. Physical Review Letters 112 (1), 013601 (2014)

. Physical Review A 95, 023832 (2017)

. Physical Review Letters 126 (24), 243901 (2021)

. Physical Review Letters 129 (9), 093603 (2022)

. Physical Review Letters 132 (12), 126901 (2024)

In optomechanics, sensors have a dual nature: mechanical and optical. They are distinguished by their sensitivity and temporal resolution. Sensitivity results from the nanometric dimensions of the devices, and from the principle of optical interferometric cavity. Temporal resolution results from the high mechanical frequencies and the gigantic bandwidth of optical techniques. Finally, in the quantum regime, optomechanical sensors are limited only by the fundamental laws of quantum physics.

In our sensors, an external disturbance produced by the environment is detected, often by measuring a mechanical or optical frequency shift. In the optomechanical disks and rings we use, it is also possible to track several mechanical and optical modes in optical modes in parallel, in order to reconstruct the information more accurately.

Individual nanoparticles, about the size of a virus, are landing one by one on an optomechanical disk that measures their mass and elasticity.

We have applied these principles to measure the mass and elasticity of a single nano-particle interacting with an optomechanical sensor, then to measure inert viruses, and finally to measure the dynamics of individual living biological objects.

We are also developing an optomechanical probe and a dedicated microscope for measuring atomic forces, with a mechanical frequency in the gigahertz range. The ambition is to measure chemical interactions with nanosecond time resolution.

Optomechanical technologies should open up new experimental windows in molecular biology and the study of protein dynamics. These fields are crucial to our understanding of the mechanisms of the living.

List of our key publications on the subject:

. Nanoscale 12 (5), 2939-2945 (2020)

. Nature Nanotechnology 15 (6), 469-474 (2020)

. Physical Review Applied 14 (2), 024079 (2020)

. Nano Letters 22 (2), 710-715 (2022)

. Microsystems & Nanoengineering 8 (1), 32 (2022)