46 research outputs found
Physics of quantum light emitters in disordered photonic nanostructures
Nanophotonics focuses on the control of light and the interaction with matter
by the aid of intricate nanostructures. Typically, a photonic nanostructure is
carefully designed for a specific application and any imperfections may reduce
its performance, i.e., a thorough investigation of the role of unavoidable
fabrication imperfections is essential for any application. However, another
approach to nanophotonic applications exists where fabrication disorder is used
to induce functionalities by enhancing light-matter interaction. Disorder leads
to multiple scattering of light, which is the realm of statistical optics where
light propagation requires a statistical description. We review here the recent
progress on disordered photonic nanostructures and the potential implications
for quantum photonics devices.Comment: Review accepted for publication in Annalen der Physi
Two mechanisms of disorder-induced localization in photonic-crystal waveguides
Unintentional but unavoidable fabrication imperfections in state-of-the-art
photonic-crystal waveguides lead to the spontaneous formation of
Anderson-localized modes thereby limiting slowlight propagation and its
potential applications. On the other hand, disorder-induced cavities offer an
approach to cavity-quantum electrodynamics and random lasing at the nanoscale.
The key statistical parameter governing the disorder effects is the
localization length, which together with the waveguide length determines the
statistical transport of light through the waveguide. In a disordered
photonic-crystal waveguide, the localization length is highly dispersive, and
therefore, by controlling the underlying lattice parameters, it is possible to
tune the localization of the mode. In the present work, we study the
localization length in a disordered photonic-crystal waveguide using numerical
simulations. We demonstrate two different localization regimes in the
dispersion diagram where the localization length is linked to the density of
states and the photon effective mass, respectively. The two different
localization regimes are identified in experiments by recording the
photoluminescence from quantum dots embedded in photonic-crystal waveguides.Comment: Accepted for publication in Physical Review
Nonuniversal intensity correlations in 2D Anderson localizing random medium
Complex dielectric media often appear opaque because light traveling through
them is scattered multiple times. Although the light scattering is a random
process, different paths through the medium can be correlated encoding
information about the medium. Here, we present spectroscopic measurements of
nonuniversal intensity correlations that emerge when embedding quantum emitters
inside a disordered photonic crystal that is found to Anderson-localize light.
The emitters probe in-situ the microscopic details of the medium, and imprint
such near-field properties onto the far-field correlations. Our findings
provide new ways of enhancing light-matter interaction for quantum
electrodynamics and energy harvesting, and may find applications in
subwavelength diffuse-wave spectroscopy for biophotonics
Single-Photon Superradiance from a Quantum Dot.
We report on the observation of single-photon superradiance from an exciton in a semiconductor quantum dot. The confinement by the quantum dot is strong enough for it to mimic a two-level atom, yet sufficiently weak to ensure superradiance. The electrostatic interaction between the electron and the hole comprising the exciton gives rise to an anharmonic spectrum, which we exploit to prepare the superradiant quantum state deterministically with a laser pulse. We observe a fivefold enhancement of the oscillator strength compared to conventional quantum dots. The enhancement is limited by the base temperature of our cryostat and may lead to oscillator strengths above 1000 from a single quantum emitter at optical frequencies
Transparent decision support for mechanical ventilation using visualization of clinical preferences
BACKGROUND: Systems aiding in selecting the correct settings for mechanical ventilation should visualize patient information at an appropriate level of complexity, so as to reduce information overload and to make reasoning behind advice transparent. Metaphor graphics have been applied to this effect, but these have largely been used to display diagnostic and physiologic information, rather than the clinical decision at hand. This paper describes how the conflicting goals of mechanical ventilation can be visualized and applied in making decisions. Data from previous studies are analyzed to assess whether visual patterns exist which may be of use to the clinical decision maker. MATERIALS AND METHODS: The structure and screen visualizations of a commercial clinical decision support system (CDSS) are described, including the visualization of the conflicting goals of mechanical ventilation represented as a hexagon. Retrospective analysis is performed on 95 patients from 2 previous clinical studies applying the CDSS, to identify repeated patterns of hexagon symbols. RESULTS: Visual patterns were identified describing optimal ventilation, over and under ventilation and pressure support, and over oxygenation, with these patterns identified for both control and support modes of mechanical ventilation. Numerous clinical examples are presented for these patterns illustrating their potential interpretation at the bedside. CONCLUSIONS: Visual patterns can be identified which describe the trade-offs required in mechanical ventilation. These may have potential to reduce information overload and help in simple and rapid identification of sub-optimal settings. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12938-021-00974-5
Resonant Photonic Quasicrystalline and Aperiodic Structures
We have theoretically studied propagation of exciton-polaritons in
deterministic aperiodic multiple-quantum-well structures, particularly, in the
Fibonacci and Thue-Morse chains. The attention is concentrated on the
structures tuned to the resonant Bragg condition with two-dimensional
quantum-well exciton. The superradiant or photonic-quasicrystal regimes are
realized in these structures depending on the number of the wells. The
developed theory based on the two-wave approximation allows one to describe
analytically the exact transfer-matrix computations for transmittance and
reflectance spectra in the whole frequency range except for a narrow region
near the exciton resonance. In this region the optical spectra and the
exciton-polariton dispersion demonstrate scaling invariance and self-similarity
which can be interpreted in terms of the ``band-edge'' cycle of the trace map,
in the case of Fibonacci structures, and in terms of zero reflection
frequencies, in the case of Thue-Morse structures.Comment: 13 pages, 9 figures, submitted to Phys. Rev.
Roadmap on all-optical processing
The ability to process optical signals without passing into the electrical domain has always attracted the attention of the research community. Processing photons by photons unfolds new scenarios, in principle allowing for unseen signal processing and computing capabilities. Optical computation can be seen as a large scientific field in which researchers operate, trying to find solutions to their specific needs by different approaches; although the challenges can be substantially different, they are typically addressed using knowledge and technological platforms that are shared across the whole field. This significant know-how can also benefit other scientific communities, providing lateral solutions to their problems, as well as leading to novel applications. The aim of this Roadmap is to provide a broad view of the state-of-the-art in this lively scientific research field and to discuss the advances required to tackle emerging challenges, thanks to contributions authored by experts affiliated to both academic institutions and high-tech industries. The Roadmap is organized so as to put side by side contributions on different aspects of optical processing, aiming to enhance the cross-contamination of ideas between scientists working in three different fields of photonics: optical gates and logical units, high bit-rate signal processing and optical quantum computing. The ultimate intent of this paper is to provide guidance for young scientists as well as providing research-funding institutions and stake holders with a comprehensive overview of perspectives and opportunities offered by this research field