arXiv subjects

Agnès Maître

Publications and source records attributed to Agnès Maître.

13 recordsLinked to original sources

arXiv2025

Feature-Resolved Photoluminescence Analysis: Probing Emission Beyond Conventional Photon Statistics

We present a feature-resolved methodology to analyse the photoluminescence dynamics of single emitters using a combination of lifetime, spectral, and photon correlation analyses. By integrating conventional ensemble photon statistics measurements with emission state-resolved, spectrally filtered, and lifetime-gated methods, we uncover emission dynamics that remain hidden in ensemble treatment. We study the fluorescence of single CdSe/CdS core/shell colloidal quantum dots under varying excitation powers. Using feature-resolved analysis, we understand the radiative and non-radiative recombination processes, and estimate quantum parameters. Event-selective analysis provides a versatile toolkit for characterizing emitters, both single and aggregate particles. These methods are broadly applicable to a wide class of photoluminescent emitters, such as nitrogen vacancy centres in nanodiamond, epitaxial quantum dots, and perovskite nanocrystals. The application of these lateral investigation techniques will contribute to the advancement of quantum light source development.

physics.optics↗

arXiv2024

Optical and X-ray Photo-emission Spectroscopies of Core/Shell Colloidal CdSe/CdS Quantum Dots: Modeling and Experimental Determination of Band Alignment

Optical properties of multilayer semi-conductor nano-emitters are crucially dependent on the relative energy levelsof their different components. For core/shell quantum dots, the relative energy difference between conduction bandedge of core and shell materials induces, depending on its value, either a confinement of the electron within the coreor a delocalization of its wave function within the whole quantum dot. This results in drastic consequences on theenergy and the oscillator strength of the fundamental transition. Surprisingly, the literature currently lacks a definitivevalue for the energy difference between CdSe and CdS conduction band edges as most of the experimental studiesprovide values corresponding to specific geometries of quantum dots. Here, we develop a full theoretical modelexpressing energy levels considering core/shell interface pressure, ligands and enabling the accurate prediction ofthe bandgap value with the nanocrystal size. It allows to reliably determine the energy difference between theconduction band edge of CdSe and CdS materials, known as the conduction band offset, in such a way that this valuecan later be used to model quantum dots of any geometry. This value is determined using our model and two differentexperimental methods: optical spectroscopy and X-ray photoemission (XPS) experiments.

cond-mat.mtrl-sci↗

arXiv2021

Efficient single-emitter plasmonic patch antenna fabrication by novel deterministic in situ optical lithography using spatially modulated light

Single-emitter plasmonic patch antennas are room-temperature deterministic single photon sources, which exhibit highly accelerated and directed single photon emission. However, for efficient operation these structures require three-dimensional nanoscale deterministic control of emitter positioning within the device, which is a demanding task, esp. when emitter damage during fabrication is a major concern. To overcome this limitation, our deterministic room-temperature in situ optical lithography protocol uses spatially modulated light to position a plasmonic structure non-destructively on any selected single-emitter with three-dimensional nanoscale control. In this paper we analyze the emission statistics of such plasmonic antennas that embed a deterministically positioned single colloidal CdSe/CdS quantum dot that highlight acceleration and brightness of emission. We demonstrate that the antenna induces a 1000-fold increase in the emitter absorption cross-section, and under high pumping, these antennas show nonlinearly enhanced emission.

physics.optics↗

arXiv2020

Fourier-imaging of single self-assembled CdSe nanoplatelet chains and clusters reveals out-of-plane dipole contribution

Fluorescent semiconductor nanoplatelets (epitaxial quantum wells) can be synthesized with excellent monodispersity and self-assembled in highly-ordered structures. Modifications of their electronic and luminescence properties when stacked, due to strong mechanical, electronic or optical interactions between them, have been the topic of intense recent discussions. In this paper, we use Fourier imaging to measure the different dipole components of various nanoplatelet assemblies. By comparing different measurement conditions and corroborating them with polarimetric analysis, we confirm an excellent precision on the dipole components. For single nanoplatelets, only in-plane dipoles (parallel to the platelet plane) are evidenced. For clusters of 2-10 platelets and chains of 30-300 platelets, on the other hand, a clear out-of-plane dipole component is demonstrated. Its contribution becomes more significant as the number of platelets is increased. We review possible explanations and suggest that the added out-of-plane dipole can be induced by strain-induced nanoplatelet deformations.

physics.optics↗

arXiv2018

Extreme multiexciton emission from deterministically assembled single emitter subwavelength plasmonic patch antennas

Plasmonic antennas are attractive optical structures for many applications in nano and quantum technologies. By providing enhanced interaction between a nanoemitter and light, they efficiently accelerate and direct spontaneous emission. One challenge, however, is the precise nanoscale positioning of the emitter in the structure. Here we present a laser etching protocol that deterministically positions a single colloidal CdSe/CdS core/shell quantum dot emitter inside a subwavelength plasmonic patch antenna with three-dimensional nanoscale control. By exploiting the properties of metal-insulator-metal structures at the nanoscale, the fabricated single emitter antenna exhibits an extremely high Purcell factor (>72) and brightness enhancement by a factor of 70. Due to the unprecedented quenching of Auger processes and the strong acceleration of multiexciton emission, more than 4 photons per pulse can be emitted by a single quantum dot. Our technology permits the fabrication of bright room-temperature single-emitter sources emitting either multiple or single photons.

quant-ph↗

arXiv2016

Plasmonics of opalic surface: a combined near-and far-field approach

An opalic plasmonic sample, constituted by a hexagonal arrangement of metallized silica spheres, presents remarkable optical properties due to the mixing of periodic arrangement and singularities at the sphere touching points. It is therefore an interesting candidate for exploiting the excitation of both localized and propagating surface plasmons. Several channels of excitation based on these properties or exploiting a certain level of disorder are evidenced, opening new routes for the efficient excitation of plasmons on a wide spectral range. The versatility of such hybrid system is evidenced in the context of two complementary experiments: specular reflective spectrometry and photoemission electron microscopy. Both techniques offer different points of view on the same physical phenomenon and the link between them is discussed. Such experiments evidence the opportunities offered by these 2D hybrid materials in the context of nanophotonics.

physics.optics↗

arXiv2016

Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials

We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance $ \ll λ$) to the far-field regime (distance $\gg λ$). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

physics.optics↗

arXiv2014

Polarimetry-based analysis of dipolar transitions of single colloidal CdSe/CdS dot-in-rods

We prove experimentally, upon polarization analysis performed on a large statistic of single nanoemitters, that high quality core/shell CdSe/CdS dot-in-rods behave as linear dipoles. Moreover, the dipole in-plane and out-of-plane orientations could be assessed. We demonstrate in particular that, contrary to expectations, the emitting dipole is not aligned with the elongated axis of the dot-in-rod. Besides, the polarimetric measurements prove that the excitation transition cannot be approximated by a single linear dipole, contrary to the emission transition. Finally, we highlight that non-radiative channels of charge carrier recombination do not affect the dipolar nature of the radiative transitions.

physics.optics↗

arXiv2013

Determination of the Surface Plasmons Polaritons extraction efficiency from a self-assembled plasmonic crystal

We experimentally measure and analytically describe the fluorescence enhancement obtained by depositing CdSe/CdS nanocrystals onto a gold plasmonic crystal, a two-dimensional grating of macroscopic size obtained by gold deposition on a self-assembled opal. We show evidences of nanocrystals near-field coupling to the gold Surface Plasmons Polaritons (SPP) followed by grating-induced SPP re-emission to far-field. We develop a theoretical framework and an original method in order to evaluate, from photoluminescence experiments, the SPP extraction efficiency of a grating.

physics.optics↗

arXiv2013

Three-dimensional orientation measurement of a single fluorescent nanoemitter by polarization analysis

We demonstrate theoretically and experimentally that the three-dimensional orientation of a single fluorescent nano-emitter can be determined by polarization analysis of the emitted light (while excitation polarization analysis provides only the in-plane orientation). The determination of the emitter orientation by polarimetry requires a theoretical description including the objective numerical aperture, the 1D or 2D nature of the emitting dipole and the environment close to the dipole. We develop a model covering most experimentally relevant microscopy configurations and provide analytical relations useful for orientation measurements. We perform polarimetric measurements on high-quality core-shell CdSe/CdS nanocrystals and demonstrate that they can be approximated by two orthogonal degenerated dipoles. Finally, we show that the orientation of a dipole can be inferred by polarimetric measurement even for a dipole in the vicinity of a gold film, while in this case the well-established defocused microscopy is not appropriate.

physics.optics↗

arXiv2013

Sputtered-silica defect layer in artificial opals: tunability of highly transmitted and reflected optical modes

We propose an original and efficient method to engineer a defect between two well-ordered silica opals by sputtering silica on the top of the first one. As the amount of sputtered silica can be well controlled, it is also the case for the thickness of the layer and consequently for the spectral position of the defect mode. The optical response of these sandwich structures is studied in terms of specular reflection and transmission spectroscopy. Tunable highly transmitted and reflected optical modes are evidenced. The very good agreement between the experimental results and the simulations, run without fitting parameters, demonstrates the almost perfect order of the synthesized structures.

physics.optics↗

arXiv2008

Multimode quantum properties of a self-imaging OPO: squeezed vacuum and EPR beams generation

We investigate the spatial quantum properties of the light emitted by a perfectly spatially degenerate optical parametric oscillator (self-imaging OPO). We show that this device produces local squeezing for areas bigger than a coherence are that depends on the crystal length and pump width. Furthermore, it generates local EPR beams in the far field. We show, calculating the eigenmodes of the system, that it is highly multimode for realistic experimental parameters.

quant-ph↗

arXiv2008

Quantum limits in the measurement of very small displacements in optical images

We consider the problem of the measurement of very small displacements in the transverse plane of an optical image with a split photodetector. We show that the standard quantum limit for such a measurement, which is equal to the diffraction limit divided by the square root of the number of photons used in the measurement, cannot be overcome by use of ordinary single-mode squeezed light. We give the form of possible multimode nonclassical states of light, enabling us to enhance by orders of magnitude the resolution of such a measurement beyond the standard quantum limit.

physics.optics↗