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Despite the considerable research interest in InGaN‐based microdisk lasers, owing to their unique circular geometry distinct from vertical cavity surface‐emitting lasers (VCSEL) or edge‐emitting lasers, commercial products remain scant due to deficient performance under electrical injection. This study proposes an innovative method integrating a thin‐film configuration with a metallic undercut, significantly augmenting optical confinement, overlap factor, and thus lasing performance. This approach results in a diminished lasing threshold from 1500 to 670 Wcm−2 and a record high quality (Q) factor of 10100 under electrical injection. Strain relaxation in the metallic undercut, identified via scanning near‐field optical microscopy (SNOM), beneficially mitigates the Quantum Confined Stark Effect (QCSE), boosting the internal quantum efficiency of the laser. Furthermore, a beneficial blue‐shift in the emission spectrum aligns with the lasing peak, strengthening the Q factor. A tactfully implemented recessed top contact enables electrical injection lasing without optical performance compromise. The study provides invaluable insights for future microdisk laser technology advancements, potentially leading to specialized functionalities, including quantum optics, thereby opening new avenues for research and applications in this field. [ABSTRACT FROM AUTHOR]

This review paper presents an overview of the optical characterization techniques for Indium Gallium Nitride (InGaN) quantum well (QW) structures at a nanoscale. The two major techniques are reviewed—Electron Microscopy‐Cathodoluminescence (EM‐CL) and Scanning Near‐field Optical Microscopy (SNOM). It elucidates the critical role these methodologies play in revealing the complex properties of InGaN QWs, including their structural characteristics, optical properties, carrier dynamics, and the effects of defects and doping. The review highlights key findings from a variety of studies, demonstrating how EM‐CL and SNOM have contributed to the understanding of these micro‐/nano‐ structures and their potential applications in high‐efficiency optoelectronic devices. [ABSTRACT FROM AUTHOR]

Silver nanoparticles on a glass substrate are experimentally investigated by aperture scanning near-field optical microscopy (a-SNOM). To understand the experimental results, finite-element-method simulations are performed building a theoretical model of the a-SNOM geometry. We systematically vary parameters like aperture size, aluminum-coating thickness, tip cone angle, and tip-surface distance and discuss their influence on the near-field enhancement. All these investigations are performed comparatively for constant-height and constant-gap scanning modes. In the end, we establish a reliable and stable optical model for simulating a-SNOM measurements, which is capable of reproducing trends observed in experimental data. [ABSTRACT FROM AUTHOR]

Optical nanoantennas demonstrate the ability to confine and enhance electromagnetic fields. This ability makes nanoantennas essential tools for highresolution microscopy. The nanoantenna resonance and response can be tuned by changing their size, shape, and material as well as adjusting the probing conditions, e.g. excitation wavelength. In this paper we simulated the propagation and interaction of visible light with computer generated models of butterfly nanoantenna arrays using the finite-difference time-domain (FDTD) method. The simulations were used to understand and predict the experimental results obtained with scanning nearfield microscopy (SNOM) on commercially available samples. Simulation parameters are chosen carefully to reflect the measurement conditions. [ABSTRACT FROM AUTHOR]

Herein we investigate the character of the near-field emission of a two- (2D) and novel three-dimensional (3D) probe geometries fabricated using 3D direct laser writing lithography. Near-field scans in x–y and y–z planes were measured both before and after the deposition of hyperbolic dispersion metamaterial (HMM) to further verify the directional propagation of the high wave-vector components present in the vicinity of the structures. Additional computational and theoretical characterization forewent the actual experimental measurements, showing a promising performance, particularly for the 3D Fresnel zone plate (FZP). Overall, the experimental data documents a subwavelength resolution with a significant signal enhancement in the focal spot of the 3D FZP and highly subwavelength depth of focus. [ABSTRACT FROM AUTHOR]

Single-crystalline lead halide perovskite nanowires are emerging as promising one-dimensional blocks for nanoscience and nanotechnology, and extensive studies of nano-lasers and nano-photodetectors have been reported. However, as perfect confined structures, their optical waveguide performances have not been widely paid attention to up to now. Here, we report on the such issue on single-crystalline CsPbBr3 nanowires and quantify it by near-field optical response mappings. The waveguide is verified as total internal reflection mode at the visible band (532 nm), and its far-field end-facet coupling efficiency of 89.6% and propagation loss as low as 5.9 dB/mm are measured from the nanowire with cross-sectional geometry of ∼600 nm × 300 nm. No evident bending loss exists in naturally curved nanowires, while it usually emerges in artificial-bended ones due to the wrinkled surfaces. Naturally welded nanowire networks show significant advantages in integrated waveguides over the artificial assembled ones, due to the coupled photons at the space-confined end-facet segments. Roughened surface reasoned by lattice degradation is detrimental to propagation loss, but it provides leaked channels for waveguide coupling on nanowire surface. This work studies the optical waveguide performance of perovskite nanowires with different geometries and goes a step further for integrated nanophotonics. [ABSTRACT FROM AUTHOR]

We demonstrate the formation of the near field with non-trivial phase distribution using surface plasmon interference devices, and experimental quantitative imaging of that phase with near-field phase microscopy. The phase distribution formed with a single device can be controlled by the polarization of the external illumination and the area of the device assigned to the object wave. A comparison of the experimental data to a numerical electromagnetic model and an analytical model assigns the origin of the near-field phase to the out-of-plane electric component of surface plasmon polaritons, and also verifies the predictive power of the models. We demonstrate a formation of near-field plane waves with different propagation directions on a single device, or even simultaneously at distinct areas of a single device. Our findings open the way to the imaging and tomography of phase objects in the near field. [ABSTRACT FROM AUTHOR]

In this study, we theoretically and experimentally investigate the propagation of a second-order cylindrical vector beam through an aluminum lens which forms a tight focus at the distance of the wavelength. Simulation by the finite-difference time-domain method and the Richards–Wolf formulae produces light field distributions which coincide with experimental measurements provided with scanning near-field optical microscopy. We demonstrate that a pyramidal metallized cantilever with a hole is more sensitive to the transversal component of intensity than to the full intensity or to the Umov–Poynting vector in areas of reverse energy flow. [ABSTRACT FROM AUTHOR]

We theoretically study the broadband near-field optical spectrum of twisted bilayer graphene (TBG) at various twist angles near the magic angle using two different models. The spectrum at low Fermi energy is characterized by a series of peaks that are almost at the same energies as the peaks in the far-field optical conductivity of TBG. When the Fermi energy is near a van Hove singularity, an additional strong peak appears at finite energy in the near-field spectrum, which has no counterpart in the optical conductivity. Based on a detailed calculation of the plasmon dispersion, we show that these spectroscopic features are associated with interband and intraband plasmons, which can provide critical information about the local band structure and plasmonic excitations in TBG. The near-field peaks evolve systematically with the twist angle, so they can serve as fingerprints for identifying the spatial dependent twist angle in TBG samples. Our findings pave the way for future experimental studies of the novel optical properties of TBG in the nanoscale. [ABSTRACT FROM AUTHOR]

A scanning near-field fluorescence microscopy for in situ test is demonstrated in this letter. The scanning near-field fluorescence microscopy can be applied to commercial environmental scanning electron microscopy (ESEM) without changing the ESEM performance. The designed scanning near-field fluorescence microscopy combines the advantage of the ESEM and scanning near-field optical microscopy (SNOM). The CdSe/ZnS quantum dot samples are prepared to verify system performance. The system offers fluorescence image and topography image simultaneously with a high depth and high resolution, thus permitting further ingredient and functional research. The topography image spatial resolution and the fluorescence image spatial resolution are below 130 nm and 115 nm, respectively, with a tip aperture of ~100 nm. The image range reaches $300\,\,\times \,\,300\,\,\mu \text{m}$ by virtue of the micromanipulators and image stitching technology. [ABSTRACT FROM AUTHOR]

Purpose: Penetrating abdominal injuries caused by stabbing or firearms are rare in Germany, thus there is lack of descriptive studies. The management of hemodynamically stable patients is still under dispute. The aim of this study is to review and improve our management of penetrating abdominal injuries. Methods: We retrospectively reviewed a 10-year period from the Trauma Registry of our level I trauma center. The data of all patients regarding demographics, clinical and outcome parameters were examined. Further, charts were reviewed for FAST and CT results and correlated with intraoperative findings. Results: A total of 115 patients with penetrating abdominal trauma (87.8% men) were analyzed. In 69 patients, the injuries were caused by interpersonal violence and included 88 stab and 4 firearm wounds. 8 patients (6.9%) were in a state of shock at presentation. 52 patients (44.8%) suffered additional extraabdominal injuries. 38 patients were managed non-operatively, while almost two-thirds of all patients underwent surgical treatment. Hereof, 20 laparoscopies and 3 laparotomies were nontherapeutic. There were two missed injuries, but no patient experienced morbidity or mortality related to delay in treatment. 106 (92.2%) FAST and 91 (79.3%) CT scans were performed. Sensitivity and specificity of FAST were 59.4 and 94.2%, while those of CT were 93.2 and 85.1%, respectively. Conclusion: In hemodynamically stable patients presenting with penetrating abdominal trauma, CT is indicated and the majority of injuries can be managed conservatively. If surgical treatment is required, diagnostic laparoscopy for stable patients is feasible to avoid nontherapeutic laparotomy. [ABSTRACT FROM AUTHOR]

The surface plasmon resonance of dewetted Au structures on TiO2 substrate using physical vapor deposition and post-annealing is investigated. In this work, we employ an aperture-probe scanning near-field optical microscope (SNOM) to study the plasmonic properties of dewetted Au structures and the influence of the size, shape, and interdistance of the dewetted structures on their plasmonic behavior. This investigation is corroborated by numerical calculations performed using finite-difference time-domain (FDTD) and atomic force microscopy (AFM) to provide a realistic and direct comparison with SNOM experiments. The near-field images obtained by both experiments and simulations reveal surface plasmon resonance around Au structures which are correlated to the broadband activity in the visible light region observed by UV-Vis spectrophotometry and photoluminescence. In addition, near-field enhancement is associated with the external quantum efficiency (EQE), which shows a multi-peak response after 570 nm due higher-order modes of plasmon resonance. This broadband improvement in the visible region obtained by controlled dewetting has potential use in large-scale solar energy applications.Graphical Abstract [ABSTRACT FROM AUTHOR]

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CECT scan is considered essential for selective non-operative management (SNOM) of patients with abdominal trauma. However, CECT has its own hazards and limitations. We evaluated the safety and efficacy of selective non-operative management of patients with abdominal trauma without the mandatory use of CECT scan in a prospective study. Patients with peritonitis and ongoing intra-abdominal bleed were excluded. Consenting FAST positive, hemodynamically stable patients with blunt and penetrating abdominal trauma between 18 and 60 years of age were included and admitted for SNOM and detailed ultrasonography of the abdomen (in all) with or without CECT abdomen (selectively). Eighty-four patients with abdominal trauma were admitted during the study period. Twenty-two patients did not satisfy the inclusion criteria and 18 required immediate laparotomy based on primary survey. Remaining 44 patients were admitted for SNOM: mean ± SD age of these patients was 27 ± 8.7 years; 40 (89 %) were males. Thirty-five patients (79.54 %) sustained blunt trauma (RTI = 16, Fall = 16, others = 3) while nine patients (20.45 %) sustained penetrating trauma. SNOM without CECT was successful in 36 (81.82 %) patients. Five (11.36 %) patients underwent delayed emergency laparotomy based on clinical and detailed USG evaluation. CECT was not done in these patients. Three patients underwent CECT for various reasons; however, they were managed with SNOM. Thus, SNOM without abdominal CECT was successful in 36 (81.82 %) patients. SNOM failed in five patients but abdominal USG was sufficient. SNOM can be practised safely in patients of abdominal trauma with limited use of CECT scan. [ABSTRACT FROM AUTHOR]

In this work, we investigate the interaction of surface plasmons with a plasmonic Lüneburg lens using near field scanning optical microscopy. Gray-scale electron beam lithography is used to prepare a dome-shaped resist structure on top of a gold film. This particular shape yields the effective refractive index profile of a Lüneburg lens for surface plasmons propagating at the film surface at an energy of $\hbar \omega ={1.72}$ eV. Next to the Lüneburg lens a grating coupler is milled into the gold film with focused ion beam. The surface plasmons are launched to propagate through the lens and the near field pattern is scanned. We clearly identify a focal spot in the near field signal at the outer perimeter of the lens. In addition, we observe a beating pattern arising from further plasmon waves excited by higher orders of the grating coupler. The emergence of this beating pattern allows the detection of the plasmon's wave fronts. An analytical model was used to retrieve the properties of the participating wave components. The measured near-field pattern could be modeled very well with electromagnetic simulations applying the effective refractive index approach. [ABSTRACT FROM AUTHOR]

The optical microscope is one of the oldest scientific instruments that is still used in forefront research. Ernst Abbe’s nineteenth century formulation of the resolution limit in microscopy let generations of scientists believe that optical studies of individual molecules and resolving subwavelength structures were not feasible. The Nobel Prize in 2014 for super-resolution fluorescence microscopy marks a clear recognition that the old beliefs have to be revisited. In this article, we present a critical overview of various recent developments in optical microscopy. In addition to the popular super-resolution fluorescence methods, we discuss the prospects of various other techniques and imaging contrasts and consider some of the fundamental and practical challenges that lie ahead. [ABSTRACT FROM PUBLISHER]

A technique of cantilever based scanning near-field optical microscopy is applied. Using InP/GaInP quantum dots structures, 100nm (λ/7) spatial resolution of the technique in illumination-collection regime is tested. The possibility to obtain optical data with a subdiffraction resolution is exploited for clarifying the transversal electric field mode configuration of the radiating semiconductor laser. [ABSTRACT FROM PUBLISHER]

Raman confocal microscopy with 488 nm excitation wavelength supported with atomic force microscopy (AFM), scanning near-field optical microscopy (SNOM) and UV-Vis spectrometry was used to investigate air-dried erythrocytes (red blood cells, RBCs) in whole human blood smears. The central internal part of the cell was dominated by the laser-induced O2 dissociated oxyHb form as evidenced by the Fe2+ marker band appearing at 1356 cm−1. The existence of a thin outer layer of hemoglobin in the periphery of RBCs was assigned to hemichrome. Evidence for hemichrome includes the oxidation state marker band appearing at 1376 cm−1, the absence of FeO2 band at 570 cm−1 and a UV-Vis spectrum consistent with hemichrome. This is the first time that distributions of Fe2+/Fe3+ hemes inside the single RBC have been reported. The outer layer formation of hemichrome was additionally studied when RBCs were in contact with leucocytes and carotenoids of blood plasma. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Clinical research on penetrating injury to the buttock is sparse and largely limited to case reports and clinical series. The purpose of this paper is to provide a detailed overview of literature of the topic and to propose a basic algorithm for management of penetrating gluteal injuries (PGI). MEDLINE, EMBASE, Cochran, and CINAHL databases were employed. Thirty-seven papers were selected and retrieved for overview from 1,021 records. PGI accounts for 2-3 % of all penetrating injuries, with a mortality rate up to 4 %. Most haemodynamically stable patients will benefit from traditional wound care and selective non-operative management. When gluteal fascia injury is confirmed or suspected, a contrast-enhanced CT-scan provides the most accurate injury diagnosis. CT-scan-based angiography and endovascular interventions radically supplement assessment and management of patients with penetrating injury to the major buttock and adjacent extra-buttock arteries. Immediate life-saving damage-control surgery is indicated for patients with hypovolemic shock and signs of internal bleeding. A universal basic management algorithm is proposed. This overview shows that penetrating injury to the buttock should be regarded as a potential life-threatening injury, and therefore, patients with such injuries should be managed in trauma centres equipped with hybrid operating theatres for emergency endovascular and open surgery for multidisciplinary teams operating 24/7. [ABSTRACT FROM AUTHOR]

This paper presents a study of the behaviour as optical superlattices of periodically poled LiNbO3and LiTaO3crystals using the Scanning Near-field Optical Microscopy (SNOM) technique. The periodic ferroelectric domains were formed either by electric field poling technique or by the “off-centre Czochralski method” during crystal growth. SNOM patterns were recorded in both collective and reflective configuration, simultaneously with surface topography measurement by AFM (Atomic Force Microscopy). It has been found that regardless of the method used to create the domains, a modulation in the SNOM signal intensity is correlated with the ferroelectric domain structure. The maximum intensity of the collected or reflected SNOM light intensity is centred on the negative domains, whereas the minimum intensity is positioned on the positive domains. This result demonstrates that the modulation of the refractive index is related to the domains and not with the wall between them. [ABSTRACT FROM PUBLISHER]

Amendments have been made to International Standard ISO 18115-2:2010, extending the number of terms and, in a few cases where usage has changed, incorporating revisions. Part 2 covers 277 terms used in scanning probe microscopy as well as 98 acronyms. The terms cover words or phrases used in describing the samples, instruments and theoretical concepts involved. © 2014 Crown copyright. Surface and Interface Analysis © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Photoexcited carrier dynamics and localization potentials in Al0.86In0.14N/GaN heterostructure have been examined by time-resolved photoluminescence (PL), transient photoreflectance and scanning near-field optical spectroscopy. The large GaN and AlInN PL intensity difference, and the short AlInN PL decay and GaN PL rise times indicate efficient photoexcited carrier transfer from AlInN to GaN via sub-band edge states. Near-field PL scans and photoreflectance data show that the diameter of the localization sites and the distance between them are well below 100 nm. Majority of these states is assigned to In clusters, in which the valence band has a higher energy than the valence band in a uniform AlInN alloy. It is likely that the carrier transport through the sub-band edge states proceeds via high conductivity channels involving extended defects. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A tapered dielectric waveguide that scans, at constant height, a sample containing a viral capsid is studied by combining a lattice gas model to simulate water meniscus formation and a finite difference time domain algorithm for light propagation through the media involved. Our results show different contrasts related to different water contents and different meniscus orientations. We propose this method as a way to study water content and evaporation process in nanocavities being either biological, like viral capsides, or nonbiological, like photonic crystals. [ABSTRACT FROM AUTHOR]

Super-microscopic techniques like scanning tunnelling microscopy, atomic force microscopy or scanning near-field optical microscopy allows investigate micro- and/or nano-scale surfaces and structures. In this paper , both Environmental scanning electron microscope (ESEM) and Scanning near field optical microscope (SNOM) have been applied to more closely study of biomaterials. The results of visualization of human osteosarcoma cell line (U2OS) are compared. SNOM and ESEM yield different, however , comparable and complementary information on studied biological samples. [ABSTRACT FROM AUTHOR]

We investigate the distribution of the membrane protein complement receptor 1 (CR1/CD35) in human erythrocyte membrane ghosts using scanning near-field optical microscopy. Recent studies have demonstrated that levels of Aβ peptide, associated with Alzheimers disease (AD) and present in brain and peripheral blood, vary significantly when bound by complement C3b-dependent adherence to CR1. It is unknown why patients with AD have a markedly impaired ability to bind Aβ to CR1 via this mechanism, but one possibility is a defect in the localization and/or conformation of CR1 in the membrane. Scanning near-field optical microscopy does not require the harsh preparation of electron microscopy techniques and may therefore be better suited for measuring membrane protein distributions. The clustering phenomenon of CR1 identified in electron microscopy studies is confirmed and quantified. The standard deviation of the inter-cluster spacing of CR1 is constant (79 ± 9 nm) across erythrocytes with between 61 and 124 clusters per membrane ghost. [ABSTRACT FROM AUTHOR]

Band gap fluctuations and carrier localization in AlxGa1-xN films with x values varying from 0.30 to 0.50 has been studied by scanning near-field optical microscopy (SNOM) by measuring photoluminescence. The measurements have revealed a dual localization potential. Microscopic scale potential variations, detected by the SNOM, were most pronounced in the lower Al content samples. The nanoscopic carrier localization potentials, evaluated from the width of the photoluminescence spectra, were largest in layers with the largest AlN molar fraction. The large scale potential fluctuations were attributed to Ga rich regions close to grain boundaries or atomic layer steps. The density, size and band gap energy of these domains were found to be composition dependent. The nanoscopic potential variations have been assigned to small-scale compositional fluctuations, possibly, occurring due to formation of Al rich grains during growth. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Top-illumination tip-enhanced Raman scattering (TI-TERS) has recently emerged as a promising near-field vibrational spectroscopy method that can be adapted on an upright optical microscope. With a relatively simplified optics, TI-TERS can probe both opaque and transparent samples making them a promising tool in nanoscale chemical analysis. One of the critical components of TI-TERS is the plasmonic nano-tip used to enhance the Raman spectroscopic signature. Herein, we numerically studied the near-field optical properties of conventional gold tip (20 nm radius of curvature) and two varieties of optical antenna-based tips in the context of TI-TERS. Optical antenna-based tips included a 40-nm gold nanoparticle attached to a dielectric tip and a 50-nm equilateral gold nanotriangle attached to a dielectric tip. We evaluated the Raman enhancement spectra as a function of experimental variables such as underlying substrate and angle of the tip with respect to substrate normal. Our analysis revealed that conventional gold tip facilitates superior enhancement and optical antenna-based tips facilitate superior spectral bandwidth and lateral resolution in TI-TERS configuration. Tips with higher enhancement can be harnessed for ultra-sensitive measurements, and tips with broader spectral bandwidth can be utilized to enhance both Stokes and anti-Stokes component of the Raman spectra. [ABSTRACT FROM AUTHOR]

A novel method combining dual wavelength fluorescent ratiometry with scanning near-field optical microscopy (SNOM) is proposed and developed to measure the concentration and distribution of protons in the vicinity of biological samples. This method involves immersing mitochondria in a pH-sensitive fluorescent dye solution instead of injecting the dye into the surface of the mitochondrial membrane. It uses a dual emission pH-sensitive dye and SNOM with a thermally pulled and metal-coated optical fiber probe to improve the spatial resolution. The time dependence of the fluorescence intensity ratio (FIR) under acid addition and the response of mitochondria to nutritional supplementation were studied by using this method. Activation of mitochondria and a distance-dependent delay in the FIR response were observed. The results confirmed that mitochondrial activity could be observed by using this method. [ABSTRACT FROM AUTHOR]

We investigate the performance of a simple corrugated aperture scanning near-field optical microscope (SNOM) probe with various cladding metals. The probes have only one corrugation, however, they offer increased transmission over both uncorrugated probes and those with many grooves. Enhancement of light throughput results from excitation of surface plasmons at the corrugation at the core-cladding interface. We show how the choice of metal influences radiation properties of grooved probes. [ABSTRACT FROM AUTHOR]

The article focuses on the study of super-resolution capability of scanning near-field optical microscopy (SNOM) with a gold particle. It mentions that a gold particle is commonly preferred as a SNOM probe due to its chemical stability. It computes the SNOM signal through two dimensional finite-difference time-domain (2D FDTD) method. It notes that an optically trapped gold particle is effective in examining the physical property of a small surface beyond the diffraction limit.

Over the past decade, interest about metal halide perovskites has rapidly increased, as they can find wide application in optoelectronic devices. Nevertheless, although thermal evaporation is crucial for the development and engineering of such devices based on multilayer structures, the optical properties of thermally deposited perovskite layers (spontaneous and amplified spontaneous emission) have been poorly investigated. This paper is a study from a nano- to micro- and macro-scale about the role of light-emitting species (namely free carriers and excitons) and trap states in the spontaneous emission of thermally evaporated thin layers of CH3NH3PbBr3 perovskite after wet air UV light trap passivation. The map of light emission from grains, carried out by SNOM at the nanoscale and by micro-PL techniques, clearly indicates that free and localized excitons (EXs) are the dominant light-emitting species, the localized excitons being the dominant ones in the presence of crystallites. These species also have a key role in the amplified spontaneous emission (ASE) process: for higher excitation densities, the relative contribution of localized EXs basically remains constant, while a clear competition between ASE and free EXs spontaneous emission is present, which suggests that ASE is due to stimulated emission from the free EXs. [ABSTRACT FROM AUTHOR]

This article presents a recent approach of polymer microtips integrated at the extremity of optical fibers by photopolymerization. The method is simple and flexible, and the obtained polymer/fiber hybrid system behaves as either a high quality microlens or a probe for near-field microscopy that requires strongly confined fields. Polymer-tipped optical fibers have been shown to be powerful in improving efficiency of coupling with laser diodes and silicon on insulator integrated guides. Finally, it is shown that the hybrid system can be used for high resolution scanning optical microscopy. [ABSTRACT FROM AUTHOR]

We explain the mechanism of defect screening in GaInN/GaN quantum wells, which are used as active layers in white and blue light emitting diodes (LEDs). Despite the fact that these devices have now been commercially available for some time, the reason for the high luminescence efficiency had not been really understood. The high defect densities in these devices commonly would not allow the use as an optical emitter. We present the mechanism turning an actually poor-quality material into a powerful optical emitter. [ABSTRACT FROM AUTHOR]

Amplitude and phase measurements of the near-field generated by isolated subwavelength apertures in a gold film are presented. The near-field distribution of such a structure is complex and the measured signal strongly depends on the electric field components effectively detected by the experimental setup. By comparing this signal with 3D vectorial calculations we are able to determine which electric field components are effectively measured. The sensitivity of the phase distribution is key to this measurement. The proposed characterization technique should prove extremely useful to calibrate a Scanning near-field optical microscopy (SNOM) beforehand in order to retrieve quantitative information on the polarization of the field distribution under study. [ABSTRACT FROM AUTHOR]

We present the implementation of a tapping-mode aperture scanning near-field optical microscope (Tapping-SNOM) to a Binder CB incubator (Istituto di Struttura della Materia, Rome, Italy). The microscope operates in the intermittent contact mode using a nonbent optical fibre allowing to reduce the perturbation exerted on the sample, while the incubator maintains a constant temperature, humidity and CO2 level. This instrument can maintain and analyse in a controlled environment different samples, both organic and nonorganic. In particular, the Tapping-SNOM can study different cell lines at nanometric resolution and in physiological buffer, following the evolution of the living cells almost indefinitely. We will present several examples of the capabilities of the tapping scanning near-field optical microscope in the study of different lines of living cells, showing corresponding topographical, optical or phase-lag images of the live samples, evidencing the excellent stability, versatility and resolution of the system. [ABSTRACT FROM AUTHOR]

Porous glass-ceramics is an extremely important material to be used in combination with metallic nanolayers as a Surface-Enhanced Raman Scattering (SERS) substrate for biological and chemical analysis, demonstrating excellent biocompatibility and chemical inertness. These materials show their own Raman background signal lateral distribution, mostly from crystalline skeleton, which has to be considered. A nano-Raman setup using the optical fibre of a Scanning Near-Field Optical Microscope (SNOM), working in collection mode, is described and applied for mapping of such glass-ceramic. The collected Raman signal of Ti and P containing phase distribution in this near-field geometry reaches spatial resolution around 50 nm. [ABSTRACT FROM AUTHOR]

We report on local photo-induced oxidation of porous silicon in water at room temperature. Starting from a nonluminescent sample, the oxidation process induces luminescence which was found to first increase and then decrease as a function of the oxidation time. A clear blue shift is also observed. This effect is believed to be owing to size modification of silicon nanocrystallites and thus is explained in terms of quantum confinement. Optical near-field images and spectrum are used to monitor the photoluminescence modifications after oxidation. As the photoluminescence can be widely tuned in wavelength and intensity, this method offers a way to pattern the emission properties of the sample. [ABSTRACT FROM AUTHOR]

In this work, we report a method to observe soft X-ray radiographs at nanoscale of various kind of samples, biological and metallic, stored in a thin layer of lithium fluoride, employing scanning near-field optical microscopy with an optical resolution that reaches 50 nm. lithium fluoride material works as a novel image detector for X-ray nano-radiographs, due to the fact that extreme ultraviolet radiation and soft X-rays efficiently produce stable point defects emitting optically stimulated visible luminescence in a thin surface layer. The bi-dimensional distribution of the so-created defects depends on the local nanostructure of the investigated sample. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the local distribution and organization of the plasma membrane NADPH-oxidase (NOX) in human haematopoietic stem cell (HSC) by means of the fluorescence scanning near-field optical microscopy approach. The presence of NOX in haematopoietic stem cells is thought to have a functional role as O2 sensor and/or as low-level reactive oxygen species (ROS) producer to be used as redox messenger for controlling cell growth and differentiation. Given the harmful potential of ROS, a fine-tuning of NOX activity is needed. The high resolution imaging of haematopoietic stem cell membrane obtained in this study combined with the immunodetection of NOX indicates for this the occurrence of a cluster-organized structure. These membrane ‘rafts’-like micro-compartments may constitute localized protein aggregates whereby the assembly/activation of the NOX components are functionally integrated with upstream factors constituting signal-transduction platforms. [ABSTRACT FROM AUTHOR]

Human HaCaT cells, exposed for 24 h to a 1 mT (rms) 50 Hz sinusoidal magnetic field in a temperature-regulated solenoid, suffer detectable changes in their biochemical properties and shapes. By using infrared wavelength-selective scanning near-field optical microscopy, we observed changes in the distribution of the inner chemical functional groups and in the cell morphology with a resolution of 80–100 nm. [ABSTRACT FROM AUTHOR]

Porous glass-ceramics is an extremely important material to be used in combination with metallic nanolayers as a Surface-Enhanced Raman Scattering (SERS) substrate for biological and chemical analysis, demonstrating excellent biocompatibility and chemical inertness. These materials show their own Raman background signal lateral distribution, mostly from crystalline skeleton, which has to be considered. A nano-Raman setup using the optical fibre of a Scanning Near-Field Optical Microscope (SNOM), working in collection mode, is described and applied for mapping of such glass-ceramic. The collected Raman signal of Ti and P containing phase distribution in this near-field geometry reaches spatial resolution around 50 nm. [ABSTRACT FROM AUTHOR]

We present the implementation of a tapping-mode aperture scanning near-field optical microscope (Tapping-SNOM) to a Binder CB incubator (Istituto di Struttura della Materia, Rome, Italy). The microscope operates in the intermittent contact mode using a nonbent optical fibre allowing to reduce the perturbation exerted on the sample, while the incubator maintains a constant temperature, humidity and CO2 level. This instrument can maintain and analyse in a controlled environment different samples, both organic and nonorganic. In particular, the Tapping-SNOM can study different cell lines at nanometric resolution and in physiological buffer, following the evolution of the living cells almost indefinitely. We will present several examples of the capabilities of the tapping scanning near-field optical microscope in the study of different lines of living cells, showing corresponding topographical, optical or phase-lag images of the live samples, evidencing the excellent stability, versatility and resolution of the system. [ABSTRACT FROM AUTHOR]

We report on local photo-induced oxidation of porous silicon in water at room temperature. Starting from a nonluminescent sample, the oxidation process induces luminescence which was found to first increase and then decrease as a function of the oxidation time. A clear blue shift is also observed. This effect is believed to be owing to size modification of silicon nanocrystallites and thus is explained in terms of quantum confinement. Optical near-field images and spectrum are used to monitor the photoluminescence modifications after oxidation. As the photoluminescence can be widely tuned in wavelength and intensity, this method offers a way to pattern the emission properties of the sample. [ABSTRACT FROM AUTHOR]

In this work, we report a method to observe soft X-ray radiographs at nanoscale of various kind of samples, biological and metallic, stored in a thin layer of lithium fluoride, employing scanning near-field optical microscopy with an optical resolution that reaches 50 nm. lithium fluoride material works as a novel image detector for X-ray nano-radiographs, due to the fact that extreme ultraviolet radiation and soft X-rays efficiently produce stable point defects emitting optically stimulated visible luminescence in a thin surface layer. The bi-dimensional distribution of the so-created defects depends on the local nanostructure of the investigated sample. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the local distribution and organization of the plasma membrane NADPH-oxidase (NOX) in human haematopoietic stem cell (HSC) by means of the fluorescence scanning near-field optical microscopy approach. The presence of NOX in haematopoietic stem cells is thought to have a functional role as O2 sensor and/or as low-level reactive oxygen species (ROS) producer to be used as redox messenger for controlling cell growth and differentiation. Given the harmful potential of ROS, a fine-tuning of NOX activity is needed. The high resolution imaging of haematopoietic stem cell membrane obtained in this study combined with the immunodetection of NOX indicates for this the occurrence of a cluster-organized structure. These membrane ‘rafts’-like micro-compartments may constitute localized protein aggregates whereby the assembly/activation of the NOX components are functionally integrated with upstream factors constituting signal-transduction platforms. [ABSTRACT FROM AUTHOR]

Human HaCaT cells, exposed for 24 h to a 1 mT (rms) 50 Hz sinusoidal magnetic field in a temperature-regulated solenoid, suffer detectable changes in their biochemical properties and shapes. By using infrared wavelength-selective scanning near-field optical microscopy, we observed changes in the distribution of the inner chemical functional groups and in the cell morphology with a resolution of 80–100 nm. [ABSTRACT FROM AUTHOR]

Scanning Near-field Optical Microscope (SNOM) is based on local excitations of nanostructures deposited on a substrate (illumination mode). Ideally, the local source behaves like a dipolar emitter so that the SNOM signal is strongly similar to the fluorescence decay rates of an excited molecule that would be located at the SNOM tip position. We present here how the SNOM signal near plasmonic nanostructures can be used to analyze radiative and non-radiative contribution to the fluorescence decay rate. [ABSTRACT FROM AUTHOR]

We have performed finite element electromagnetic analysis of ‘apertureless’ scanning near-field optical microscope tips. A variety of radii was considered, from 40 nm down to 1 nm, and the enhancement of optical scattering from the region beneath the probe apex was modelled in air and water. We observed sizeable spectral shifts when the radius decreases, together with a surprising increase in the amount of scattering from small tips. The lateral resolution is considered, which is shown to be always smaller than the tip radius, and for 1-nm-radius tips can allow atomic resolution imaging with sufficient optical enhancement. Gold, silver, copper and aluminium were modelled as tip materials. [ABSTRACT FROM AUTHOR]