Push our optical trap toward a full 3D view of Brownian motion. Having proven we can track x(t) and y(t) under white light, cross-calibrated with our ultra-fast photodiode x(t) channel, join us to add a fast y(t) channel and a brand-new z(t) axis, the first steps toward a PhD probing particles near walls.

In reduced dimensionality, particles coined “anyons” can evade the familiar division between fermions and bosons with a fractional exchange phase between 0 and pi, with applications to topological quantum computation. Early on, quasiparticles of the Fractional Quantum Hall regime were identified as anyon candidates, and their fractional statistics was experimentally established in a few pioneer experiments in the early 2020s. It has been suggested that their existence extends way beyond this restrictive framework, and that they emerge for instance in bidimensional ballistic electron systems with strong Coulomb interactions, resulting in electron charge and statistics fractionalization. The goal of this internship is to follow this novel approach with quantum circuit tools, combining quantum point contacts, single electron physics at high charging energies and ballistic edge channels of the Integer quantum Hall regime. The student will learn a variety of techniques mastered in the team (ultrasensitive conductance and quantum shot noise measurements, quantum thermal transport, electron interferometry), in order to reveal the anyonic nature of the system’s excitations, and characterize their quantum coherence.

Colloidal Quantum Dots (CQDs) are size-tunable semiconductors. They received the Nobel Prize in 2023 after being integrated into displays thanks to their spectrally narrow luminescence. While visible CQDs are now commercially available, their infrared counterparts have not yet released their full potential, whereas the short-wave infrared range lacks efficient non-coherent sources. The project aims to explore the design of light-emitting diodes operating in the 1 to 5 µm range. The infrared light-emitting layer is sandwiched between charge injection layers that selectively inject electrons and holes. In the visible range, the quantum efficiency can be as high as 20%, but it quickly drops as longer wavelengths are targeted (1% at 1.3 µm and 0.1% at 2 µm) due to the lengthening of the radiative lifetime and inefficient shielding, which makes non-radiative processes dominant. Thus, new concepts need to be introduced to circumvent this drop in efficiency. The project will explore new concepts related to charge injection based on energy transfer and cascade effects as strategies to generate electrical gain. A second aspect of the project will relate to the design and fabrication of photonic structures to achieve better light outcoupling.

Design of an infrared camera from colloidal quantum dots

Light Emitting Diodes (LEDs) made of nitride materials are universally used for energy-efficient lighting. However, such LEDs suffer from drastic drops in efficiency at high current densities and high emission wavelengths (green to red), whose causes are still debated due to their complexity. Understanding them requires to access carrier behavior inside the active region of the LED itself, taking into account microscopic structuration and heterogeneities. Most approaches in the literature focus on spatially averaged measurements, missing out the core of the problem. This project proposes to develop a novel approach to directly image carrier behavior (injection, recombination et escape) in the active region of an in operando LED. The aim is to perform a pump-probe electrical and optical excitation on a cleaved device observed in cross-section in a low energy electron microscope. This approach includes several challenging steps, among them the cleavage of an operating device for an observation in cross-section and the development of a mixed electrical and optical excitation of the LED under the microscope. Numerical modelling will be developed to support experimental findings.

The goal of this internship is to develop and characterize nonlinear acousto-optic devices operating in the mid-infrared (wavelength of 3-8µm), leveraging broadband transparency and piezoelectricity of III-V semiconductor heterostructures. These devices will perform phase modulation, but also potentially on-chip optical routing, a pre-requisite for magnetic field-free optical isolation. The internship will be mostly experimental, involving the use and development of two existing setups. The first one is a mid-IR integrated photonic bench allowing to characterize the operation of the devices (see above, right). The second one is a heterodyne interferometer, that allows to image the SAW-related vibration (amplitude and phase) of the sample surface to characterize the acoustic properties of the devices (see above, left).

Description See pdf file for all the details Extremely brief summary: The goal of the internship is to develop and optimize mid-IR nonlinear mirrors, supported by recent results from the host team, that target comb operation of fiber lasers at lambda=3.5 and 4.6 um, and explore the mode locking regime. Our collaborators at CORIA/CNRS laboratory have developed these novel sources, and our SESAMs will enable their mode-locking operation

Optical levitation is a subfield of optomechanics, in which a nanoparticle is trapped in a vacuum at the focal spot of a microscope objective. Because levitated systems outperform other mechanical resonators, they offer the tantalizing prospect of investigating quantum mechanics at the mesoscale. To display quantum properties, the nanoparticle must be cooled down close to its ground state, which is typically achieved through the monitoring of its displacements and a modulation of the laser’s intensity. Currently, the most exciting endeavor in the field lays in performing levitation with many-body systems. Many-body levitation would offer the opportunity to observe effects for the first time, like the mesoscopic entanglement of nanoparticles. Sadly, conventional cooling techniques, cannot be multiplexed and fail badly to cool several elements in parallel. Throughout this internship, the candidate will experimentally implement a new cooling technique intended to achieve the first-ever cooling of a many-body system composed of multiple nanoparticles in levitation. Compared to former strategies, here, a spatial light modulator is used to spatially shape the wavefront of the laser beam. Such a modulation enables to exert simultaneously adapted optical forces on all the nanoparticles in order to reduce their individual vibrational motions, which ultimately leads to the cooling of the many-body system. A funding is available to continue this internship through a PhD.

Quantum information protocols are well defined mathematically, and there exist different benchmarks for establishing the necessary resources for potential quantum advantage, as for instance the discrete Wigner function negativies or "magic". At the same time, physical systems, and in particular, bosonic systems - as the quantum electromagnetic field - can be used to encode quantum information or, alternatively speaking, simulate quantum informational protocols. Nevertheless, for such systems, the "magical" resources enabling quantum advantage over classical simulations - i.e., enabling the efficient simulation of quantum protocols - are subjected to physical constraints, as symmetries and conservation laws. While abstract qubits have no particular symmetry, photons are bosons, symmetric identical particles. During this internship, we will address the interplay between physical and informational resources to determine how detection may be seen as a non-classical resource in quantum optics based quantum information protocols. This will be done by constructing a original framework where the phase reference of quantum optical states is explicitly treated as a resource. In general, this resource is implicit and disregarded, obscuring the assessment of the resource tradeoff of bosonic quantum information protocols. We will analyze, in particular, the role of detection in BosonSampling protocols and in homodyne detection, that is usually considered as resourceless.

See pdf file for all the details Extreme brief summary: The goal of the internship is to develop electrically reconfigurable meta-surfaces whose optical properties, in reflection/ absorption, can be addressed electrically on ultra-fast timescales. In particular, we target ultra-fast amplitude modulators for the mid-infrared spectral range. These developments are crucial for applications such as laser phase stabilization, spectroscopy, frequency comb generation, mode-locking, optical communications.

The goal of the internship is to develop an optical spectroscopy technique that is spatially resolved at the nanoscale, which is known as tip-enhanced photoluminescence (TEPL). This technique employs a laser beam focused onto the apex of a plasmonic metal tip (gold or silver) within an atomic force microscope (AFM) or scanning tunneling microscope (STM). To maximize the field enhancement effect at the tip apex, the focused beam must be radially polarized. To achieve this specific polarization, the intern will use a liquid-crystal polarization converter. The intern will then couple this beam to the plasmonic tip of an AFM or STM microscope, contribute to developing the software interface for controlling the optical detectors, and conduct TEPL experiments on semiconductor nanomaterial samples.

The objective of the internship and the thesis is to investigate the combined effect of nonlinearities and complex interferences in these optical graphs, particularly regarding the formation and dynamics of soliton states. In a second time, we will inject non-classical light (squeezed light or entangled photons) to test if entanglement is sensitive to chaos.

Photonic time crystals -optical systems that are strongly and periodically modulated in time- have recently emerged as a novel paradigm for controlling light–matter interactions through temporal modulation, analogous to how conventional spatial photonic crystals manipulate light through spatial structuring. Building on our recent demonstration of a photonic time crystal using a plasmonic metamaterial operating at Terahertz frequencies, this internship aims to lay the groundwork for realizing a quantum plasmonic metamaterial time crystal, that is a photonic time crystal that can operate in the few-photon regime. This will require developing a Terahertz spectroscopy setup with extended frequency coverage as well as the design and characterization of advanced plasmonic metamaterials.

In this project we will (1) locally and electrically excite chiral plasmonic nanoparticles and (2) to use them to enhance the chiral properties of a new class of two-dimensional (2D) semiconductors called transition metal dichalcogenides (TMDCs), which are key for a new branch of physics and technology called valleytronics