Direct Measurement of the Local Density of Optical States in the Time Domain.

One of the most fundamental and relevant properties of a photonic system is the local density of optical states (LDOS) as it defines the rate at which an excited emitter dissipates energy by coupling to its surrounding. However, the direct determination of the LDOS is challenging as it requires measurements of the complex electric field of a point dipole at its own position. We introduce here a near-field setup which can measure the terahertz electric field amplitude at the position of a point source in the time domain.

Highly Ordered Supramolecular Materials of Phase-Separated Block Molecules for Long-Range Exciton Transport.

Efficient energy transport over long distances is essential for optoelectronic and light-harvesting devices. Although self-assembled nanofibers of organic molecules are shown to exhibit long exciton diffusion lengths, alignment of these nanofibers into films with large, organized domains with similar properties remains a challenge. Here, it is shown how the functionalization of C -symmetric carbonyl-bridged triarylamine trisamide (CBT) with oligodimethylsiloxane (oDMS) side chains of discrete length leads to fully covered surfaces with aligned domains up to 125 × 70 µm in which long-range exciton transport takes place.

Impact of indirect transitions on valley polarization in WS and WSe.

Controlling the momentum of carriers in semiconductors, known as valley polarization, is a new resource for optoelectronics and information technologies. Materials exhibiting high polarization are needed for valley-based devices. Few-layer WS shows a remarkable spin-valley polarization above 90%, even at room temperature.

High-Frequency Sheet Conductance of Nanolayered WS Crystals for Two-Dimensional Nanodevices.

Time-resolved terahertz (THz) spectroscopy is a powerful technique for the determination of charge transport properties in photoexcited semiconductors. However, the relatively long wavelengths of THz radiation and the diffraction limit imposed by optical imaging systems reduce the applicability of THz spectroscopy to large samples with dimensions in the millimeter to centimeter range. Exploiting THz near-field spectroscopy, we present the first time-resolved THz measurements on a single exfoliated 2D nanolayered crystal of a transition metal dichalcogenide (WS).

Chasing Vibro-Polariton Fingerprints in Infrared and Raman Spectra Using Surface Lattice Resonances on Extended Metasurfaces.

We present an experimental investigation of vibrational strong coupling of C=O bonds in poly(methyl methacrylate) to surface lattice resonances (SLRs) on arrays of gold particles in infrared and Raman spectra. SLRs are generated from the enhanced radiative coupling of localized resonances in single particles by diffraction in the array. Compared to previous studies in Fabry-Perot cavities, particle arrays provide a fully open system that easily couples with external radiation while having large field confinement close to the array.

Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging.

Bound states in the continuum (BICs) represent a new paradigm in photonics due to the full suppression of radiation losses. However, this suppression has also hampered the direct observation of them. By using a double terahertz (THz) near-field technique that allows the local excitation and detection of the THz amplitude, we are able to map for the first time the electromagnetic field amplitude and phase of BICs over extended areas, unveiling the field-symmetry protection that suppresses the far-field radiation.

Fröhlich interaction dominated by a single phonon mode in CsPbBr.

The excellent optoelectronic performance of lead halide perovskites has generated great interest in their fundamental properties. The polar nature of the perovskite lattice means that electron-lattice coupling is governed by the Fröhlich interaction. Still, considerable ambiguity exists regarding the phonon modes that participate in this crucial mechanism.

Spatial coherence from Nd quantum emitters mediated by a plasmonic chain.

Controlling the coherence properties of rare earth emitters in solid-state platforms in the absence of an optical cavity is highly desirable for quantum light-matter interfaces and photonic networks. Here, we demonstrate the possibility of generating directional and spatially coherent light from Nd ions coupled to the longitudinal plasmonic mode of a chain of interacting Ag nanoparticles. The effect of the plasmonic chain on the Nd emission is analyzed by Fourier microscopy.

Effective Negative Diffusion of Singlet Excitons in Organic Semiconductors.

Using diffraction-limited ultrafast imaging techniques, we investigate the propagation of singlet and triplet excitons in single-crystal tetracene. Instead of an expected broadening, the distribution of singlet excitons narrows on a nanosecond time scale after photoexcitation. This narrowing results in an effective negative diffusion in which singlet excitons migrate toward the high-density region, eventually leading to a singlet exciton distribution that is smaller than the laser excitation spot.

Correlated Exciton Fluctuations in a Two-Dimensional Semiconductor on a Metal.

Excitons in nanoscale materials can exhibit fluorescence fluctuations. Intermittency is pervasive in zero-dimensional emitters such as single molecules and quantum dots. In contrast, two-dimensional semiconductors are generally regarded as stable light sources.

Ultrafast Dynamics of Nonequilibrium Organic Exciton-Polariton Condensates.

Exciton-polariton condensation in organic materials, arising from the coupling of Frenkel excitons to the electromagnetic field in cavities, is a phenomenon resulting in low-threshold coherent light emission among other fascinating properties. The exact mechanisms leading to the thermalization of organic exciton-polaritons toward condensation are not yet understood, partly due to the complexity of organic molecules and partly to the canonical microcavities used in condensation studies, which limit broadband studies. Here, we exploit an entirely different cavity design, i.

Coherent Control of the Optical Absorption in a Plasmonic Lattice Coupled to a Luminescent Layer.

We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin luminescent layer.

Directional sideward emission from luminescent plasmonic nanostructures.

Periodic arrays of metallic nanoparticles can be used to enhance the emission of light in certain directions. We fabricated hexagonal arrays of aluminium nanoparticles combined with thin layers of luminescent material and optimized period (275 nm) and thickness (1500 nm) to obtain sideward directional emission into glass for a wavelength band around 620 nm. The key physics is that the luminescent layer acts as a waveguide, from which light is emitted at preferential angles using diffractive effects.

Enhanced THz extinction in arrays of resonant semiconductor particles.

We demonstrate experimentally the enhanced THz extinction by periodic arrays of resonant semiconductor particles. This phenomenon is explained in terms of the radiative coupling of localized resonances with diffractive orders in the plane of the array (Rayleigh anomalies). The experimental results are described by numerical calculations using a coupled dipole model and by Finite-Difference in Time-Domain simulations.

Modulated light absorption and emission of a luminescent layer by phase-controlled multiple beam illumination.

We propose a multiple beam illumination scheme to control the intensity of the light emitted by a thin luminescent layer. The experiment is designed to get as close as possible to the condition of Coherent Perfect Absorption (CPA) at a wavelength at which the absorption coefficient of the luminescent layer is low, and it is realized by externally acting on the phase difference between the incident beams. We elucidate experimental limitations that prevent the achievement of CPA in these slabs.

Cadaveric bone marrow mesenchymal stem cells: first experience treating a patient with large severe burns.

Background: In January 2005, Rasulov et al. originally published "First experience in the use of bone marrow mesenchymal stem cells (MSCs) for the treatment of a patient with deep skin burns". Here, we present the first ever treated patient with cadaveric bone marrow mesenchymal stem cells (CMSCs) in the history of Medicine.

Long-range guided THz radiation by thin layers of water.

We propose a novel method to guide THz radiation with low losses along thin layers of water. This approach is based on the coupling of evanescent surface fields at the opposite sides of the thin water layer surrounded by a dielectric material, which leads to a maximum field amplitude at the interfaces and a reduction of the energy density inside the water film. In spite of the strong absorption of water in this frequency range, calculations show that the field distribution can lead to propagation lengths of several centimeters.

Modified light emission from emitters coupled to long-range guided modes in strongly absorbing layers.

We demonstrate the near-field coupling and energy transfer between photoexcited dye molecules and guided modes in layers of strongly absorbing dielectrics. The dye molecules decay by exciting long-range guided modes (LRGMs) in a thin layer of chalcogenide glass. These modes can exist in spite of the very large absorption of the material forming the layer.

Selective detection of bacterial layers with terahertz plasmonic antennas.

Current detection and identification of micro-organisms is based on either rather unspecific rapid microscopy or on more accurate but complex and time-consuming procedures. In a medical context, the determination of the bacteria Gram type is of significant interest. The diagnostic of microbial infection often requires the identification of the microbiological agent responsible for the infection, or at least the identification of its family (Gram type), in a matter of minutes.

Detection of deep-subwavelength dielectric layers at terahertz frequencies using semiconductor plasmonic resonators.

Plasmonic bowtie antennas made of doped silicon can operate as plasmonic resonators at terahertz (THz) frequencies and provide large field enhancement close to their gap. We demonstrate both experimentally and theoretically that the field confinement close to the surface of the antenna enables the detection of ultrathin (100 nm) inorganic films, about 3750 times thinner than the free space wavelength. Based on model calculations, we conclude that the detection sensitivity and its variation with the thickness of the deposited layer are related to both the decay of the local THz field profile around the antenna and the local field enhancement in the gap of the bowtie antenna.

Controlling the directional emission of light by periodic arrays of heterostructured semiconductor nanowires.

We demonstrate experimentally the directional emission of light by InAsP segments embedded in InP nanowires. The nanowires are arranged in a periodic array, forming a 2D photonic crystal slab. The directionality of the emission is interpreted in terms of the preferential decay of the photoexcited nanowires and the InAsP segments into Bloch modes of the periodic structure.