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We demonstrate numerical refocusing in coherent confocal laser scanning microscopy based on synthetic optical holography. This physics-based approach implements a computational propagation on the complex signal recovered in synthetic holography consistent with the wave physics and the parameters of the microscope. An experimental demonstration is shown to restore an in-focus image of a test object from data acquired at several focal plane off-sets. Numerical refocusing can provide focused views on samples with large height variation with a potential application in confocal optical surface profiling.

Scattering-type scanning near-field optical microscopy (s-SNOM), and its derivate, Fourier transform infrared nanospectroscopy (nano-FTIR) are emerging techniques for infrared (IR) nanoimaging and spectroscopy with applications in diverse fields ranging from nanophotonics, chemical imaging and materials science. However, spectroscopic nanoimaging is still challenged by the limited acquisition rate of current nano-FTIR technology. Here we combine s-SNOM, nano-FTIR and synthetic optical holographic (SOH) to achieve infrared spectroscopic nanoimaging at unprecedented speed (8 spectroscopically resolved images in 20 min), which we demonstrate with a polymer composite sample. Beyond being fast, our method promises to enable nanoimaging in the long IR spectral range, which is covered by IR supercontinuum and synchrotron sources, but not by current quantum cascade laser technology., 17 pages, 4 figures, plus supplementary information

Scattering-type scanning near-field optical microscopy (s-SNOM) allows for nanoscale optical mapping of manifold material properties. It is based on interferometric recording of the light scattered at a scanning probe tip. For dielectric samples such as biological materials or polymers, the near-field amplitude and phase signals of the scattered field reveal the local reflectivity and absorption, respectively. Importantly, absorption in s-SNOM imaging corresponds to a positive phase contrast relative to a non-absorbing reference sample. Here, we describe that in certain conditions (weakly or non- absorbing material placed on a highly reflective substrate), a slight negative phase contrast may be observed, which can hinder the recognition of materials exhibiting a weak infrared absorption. We first document this effect and explore its origin using representative test samples. We then demonstrate straightforward simple correction methods that remove the negative phase contrast and that allow for the identification of weak absorption contrasts.

Plasmon polaritons in topological insulators attract attention from a fundamental perspective and for potential THz photonic applications. Although polaritons have been observed by THz far-field spectroscopy on topological insulator microstructures, real-space imaging of propagating THz polaritons has been elusive so far. Here, we show spectroscopic THz near-field images of thin Bi2Se3 layers (prototypical topological insulators) revealing polaritons with up to 12 times increased momenta as compared to photons of the same energy and decay times of about 0.48 ps, yet short propagation lengths. From the images we determine and analyze the polariton dispersion, showing that the polaritons can be explained by the coupling of THz radiation to various combinations of Dirac and massive carriers at the Bi2Se3 surfaces, massive bulk carriers and optical phonons. Our work provides critical insights into the nature of THz polaritons in topological insulators and establishes instrumentation and methodology for imaging of THz polaritons.

Plasmon polaritons in topological insulators attract attention from a fundamental perspective and for potential THz photonic applications. Although polaritons have been observed by THz far-field spectroscopy on topological insulator microstructures, real-space imaging of propagating THz polaritons has been elusive so far. Here, we show spectroscopic THz near-field images of thin Bi

Label-free imaging approaches seek to simplify and augment histopathologic assessment by replacing the current practice of staining by dyes to visualize tissue morphology with quantitative optical measurements. Quantitative phase imaging (QPI) operates with visible/UV light and thus provides a resolution matched to current practice. Here we introduce and demonstrate confocal QPI for label-free imaging of tissue sections and assess its utility for manual histopathologic inspection. Imaging cancerous and normal adjacent human breast and prostate, we show that tissue structural organization can be resolved with high spatial detail comparable to conventional H&E stains. Our confocal QPI images are found to be free of halo, solving this common problem in QPI. We further describe and apply a virtual imaging system based on Finite-Difference Time-Domain (FDTD) calculations to quantitatively compare confocal with wide-field QPI methods and explore performance limits using numerical tissue phantoms., 18 pages, 6 figures

Patient: Female, 64-year-old Final Diagnosis: Akute cholezystitis with left-sided gallbladder Symptoms: Upper abdominal pain Medication:— Clinical Procedure: Laparoscopic cholecystektomy Specialty: Surgery Objective: Congenital defects/diseases Background: A left-sided gallbladder without situs inversus is a rare congenital anomaly of the gallbladder with a prevalence ranging from 0.04–0.3%. Case Repost: We present a case of a female patient, referred to our clinic with clinical features of an acute cholecystitis. After performing the standard preoperative investigations, which confirmed the diagnosis, the patient underwent a laparoscopic cholecystectomy. We found a left-sided gallbladder, attached to the lower surface of the left lobe of the liver. During the dissection in the Callot triangle an aplastic cystic duct was also identified. The extirpation of the gallbladder was performed anterograde, allowing a better exposition of the critical structures. Conclusions: A left sided gallbladder is almost an incidental finding, which can be accompanied with further anomalies of the biliary tree. A combination of these 2 variations is very rare without any other reported cases in the literature.

Optical microscopy for biomedical samples requires expertise in staining to visualize structure and composition. Midinfrared (mid-IR) spectroscopic imaging offers label-free molecular recording and virtual staining by probing fundamental vibrational modes of molecular components. This quantitative signal can be combined with machine learning to enable microscopy in diverse fields from cancer diagnoses to forensics. However, absorption of IR light by common optical imaging components makes mid-IR light incompatible with modern optical microscopy and almost all biomedical research and clinical workflows. Here we conceptualize an IR-optical hybrid (IR-OH) approach that sensitively measures molecular composition based on an optical microscope with wide-field interferometric detection of absorption-induced sample expansion. We demonstrate that IR-OH exceeds state-of-the-art IR microscopy in coverage (10-fold), spatial resolution (fourfold), and spectral consistency (by mitigating the effects of scattering). The combined impact of these advances allows full slide infrared absorption images of unstained breast tissue sections on a visible microscope platform. We further show that automated histopathologic segmentation and generation of computationally stained (stainless) images is possible, resolving morphological features in both color and spatial detail comparable to current pathology protocols but without stains or human interpretation. IR-OH is compatible with clinical and research pathology practice and could make for a cost-effective alternative to conventional stain-based protocols for stainless, all-digital pathology.

Infrared-Optical Hybrid Microscopy (IR-OH) provides mid-IR imaging on the visible microscope platform based on photothermal expansion. Spectral IR imaging of full tissue slides is demonstrated for automated disease diagnosis and computational H&E staining.

Phonon polaritons in van der Waals materials can strongly enhance light–matter interactions at mid-infrared frequencies, owing to their extreme field confinement and long lifetimes1,2,3,4,5,6,7. Phonon polaritons thus bear potential for vibrational strong coupling with molecules. Although the onset of vibrational strong coupling was observed spectroscopically with phonon-polariton nanoresonators8, no experiments have resolved vibrational strong coupling in real space and with propagating modes. Here we demonstrate by nanoimaging that vibrational strong coupling can be achieved between propagating phonon polaritons in thin van der Waals crystals (hexagonal boron nitride) and molecular vibrations in adjacent thin molecular layers. We performed near-field polariton interferometry, showing that vibrational strong coupling leads to the formation of a propagating hybrid mode with a pronounced anti-crossing region in its dispersion, in which propagation with negative group velocity is found. Numerical calculations predict vibrational strong coupling for nanometre-thin molecular layers and phonon polaritons in few-layer van der Waals materials, which could make propagating phonon polaritons a promising platform for ultrasensitive on-chip spectroscopy and strong-coupling experiments., We acknowledge financial support from the Spanish Ministry of Science, Innovation and Universities (national projects MAT2017-88358-C3, RTI2018-094830-B-100, RTI2018-094861-B-100, and the project MDM-2016-0618 of the Maria de Maeztu Units of Excellence Program), the Basque Government (grant numbers IT1164-19 and PIBA-2020-1-0014) and the European Union’s Horizon 2020 research and innovation programme under the Graphene Flagship (grant agreement numbers 785219 and 881603, GrapheneCore2 and GrapheneCore3). F. Calavelle acknowledges support from the European Union H2020 under the Marie Skłodowska-Curie Actions (766025-QuESTech). J.T.-G. acknowledges support through the Severo Ochoa Program from the Government of the Principality of Asturias (number PA-18-PF-BP17-126). P.A.-G. acknowledges support from the European Research Council under starting grant number 715496, 2DNANOPTICA. Further, support from the Materials Engineering and Processing program of the National Science Foundation, award number CMMI 1538127 for h-BN crystal growth is greatly appreciated.

Patient: Female, 49-year-old Final Diagnosis: Echinococcus infection Symptoms: Left upper quadrant abdominal pain Medication:— Clinical Procedure: — Specialty: Surgery Objective: Rare disease Background: Extrahepatic and extrapulmonary localizations of cystic echinococcosis (CE) are rare and the incidence of splenic involvement is seen in 1.0% to 3.3% of all cases in the endemic areas of the Middle East and Asia. The diagnostic pathway consists of a detailed travel history, physical examination, abdominal ultrasonography, computed tomography, and serological tests. The efficacy of perioperative administration of albendazole (400 mg twice a day) has been proven; however, the appropriate surgical procedure for the treatment of giant, centrally located splenic hydatid cysts remains controversial. Case Report: We present the case of a 49-year-old woman referred to our hospital for a suspected isolated splenic hydatid cyst causing a compression of the right kidney, stomach, and the tail of the pancreas. She reported chronic pain in the left upper quadrant and a history of contact with animals. She underwent open splenectomy via a medial to lateral approach to minimize manipulation of the spleen. In addition, she received perioperative parasitostatic drug therapy with albendazole. The postoperative period was uneventful and the histologic analysis confirmed the diagnosis. Conclusions: The spleen is a rare location for isolated CE, especially in non-endemic areas and must be considered in the differential diagnosis of splenic cystic masses. Surgical resection remains the most effective treatment that completely resolves this condition. A comparison of randomized trials is needed to compare the recurrence rates between splenectomy and spleen-preserving procedures in the treatment of giant splenic hydatid cysts.

We present a technically simple implementation of quantitative phase imaging in confocal microscopy based on synthetic optical holography with sinusoidal-phase reference waves. Using a Mirau interference objective and low-amplitude vertical sample vibration with a piezo-controlled stage, we record synthetic holograms on commercial confocal microscopes (Nikon, model: A1R; Zeiss: model: LSM-880), from which quantitative phase images are reconstructed. We demonstrate our technique by stain-free imaging of cervical (HeLa) and ovarian (ES-2) cancer cells and stem cell (mHAT9a) samples. Our technique has the potential to extend fluorescence imaging applications in confocal microscopy by providing label-free cell finding, monitoring cell morphology, as well as non-perturbing long-time observation of live cells based on quantitative phase contrast., Comment: (c) 2019 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited. https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-5-A55

Nanofocusing of light offers new technological opportunities for the delivery and manipulation of electromagnetic fields at sub-diffraction limited length scales. Here, we show that hyperbolic phonon polarity,HPP, modes in the mid infrared as supported by a hexagonal boron nitride, h-BN, slab can be nanofocused (i.e. both field enhanced and wavelength compressed) by propagation along a vertical taper. Via numerical simulations, we demonstrate that field enhancement factors of 90, for steep tapers, and wavelength compression of more than an order of magnitude for adiabatic tapers, can be expected. Employing scatteringtype scanning near field optical microscopy ,s SNOM, we provide for the first time proof of principle experimental evidence of a significant HPP wavelength compression. We expect these functionalities to provide diverse applications, from biosensing and non-linear optics to optical circuitry., Comment: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Photonics, copyright \c{opyright} American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: https://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00186

We introduce a new modality for dynamic phase imaging in confocal microscopy based on synthetic optical holography. By temporal demultiplexing of the detector signal into a series of holograms, we record time-resolved phase images directly in the time domain at a bandwidth as determined by the photo detector and digitizer. We demonstrate our method by optical imaging of transient vibrations in an atomic force microscope cantilever with 100 ns time resolution, and observe the dynamic deformation of the cantilever surface after excitation with broadband mechanical pulses. Temporal Fourier transform of a single data set acquired in 4.2 minutes yields frequency and mode profile of all excited out-of-plane vibration modes with sub-picometer vertical sensitivity and sub-micrometer lateral resolution. Our method has the potential for transient and spectroscopic vibration imaging of micromechanical systems at nano- and picosecond scale time resolution., Comment: (c) 2019 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved. https://doi.org/10.1364/OE.26.026688

Near-field optical microscopy techniques provide information on the amplitude and phase of local fields in samples of interest in nanooptics. However, the information on the near field is typically obtained by converting it into propagating far fields where the signal is detected. This is the case, for instance, in polarization-resolved scattering-type scanning near-field optical microscopy (s-SNOM), where a sharp dielectric tip scatters the local near field off the antenna to the far field. Up to now, basic models have interpreted S- and P-polarized maps obtained in s-SNOM as directly proportional to the in-plane (Ex or Ey) and out-of-plane (Ez) near-field components of the antenna, respectively, at the position of the probing tip. Here, a novel model that includes the multiple-scattering process of the probing tip and the nanoantenna is developed, with use of the reciprocity theorem of electromagnetism. This novel theoretical framework provides new insights into the interpretation of s-SNOM near-field maps: the model reveals that the fields detected by polarization-resolved interferometric s-SNOM do not correlate with a single component of the local near field, but rather with a complex combination of the different local near-field components at each point (Ex, Ey and Ez). Furthermore, depending on the detection scheme (S- or P-polarization), a different scaling of the scattered fields as a function of the local near-field enhancement is obtained. The theoretical findings are corroborated by s-SNOM experiments which map the near field of linear and gap plasmonic antennas. This new interpretation of nanoantenna s-SNOM maps as a complex-valued combination of vectorial local near fields is crucial to correctly understand scattering-type near-field microscopy measurements as well as to interpret the signals obtained in field-enhanced spectroscopy.

Time-domain interferometry and near-field scanning microscopy are used to investigate infrared phonon polaritons exhibiting hyperbolic dispersion. Negative phase velocity and group velocity as small as 0.002c are confirmed. Polaritons with hyperbolic dispersion are key to many emerging photonic technologies, including subdiffraction imaging, sensing and spontaneous emission engineering1,2,3,4,5,6,7,8. Fundamental to their effective application are the lifetimes of the polaritons, as well as their phase and group velocities7,9. Here, we combine time-domain interferometry10 and scattering-type near-field microscopy11 to visualize the propagation of hyperbolic polaritons in space and time, allowing the first direct measurement of all these quantities. In particular, we study infrared phonon polaritons in a thin hexagonal boron nitride8,12,13 waveguide exhibiting hyperbolic dispersion and deep subwavelength-scale field confinement. Our results reveal—in a natural material—negative phase velocity paired with a remarkably slow group velocity of 0.002c and lifetimes in the picosecond range. While these findings show the polariton's potential for mediating strong light–matter interactions and negative refraction, our imaging technique paves the way to explicit nanoimaging of polariton propagation characteristics in other two-dimensional materials, metamaterials and waveguides.

We demonstrate that functional infrared transmission lines (TLs) with gap widths of 25 and 5 nm can be fabricated by gallium and helium ion beam milling of gold films thermally evaporated on insulating substrates. Interferometric and polarization-resolved scattering-type scanning near-field microscopy at λ0 = 9.3 μm is applied to image in real space the propagation and confinement of the TL modes. Mapping the p-polarized scattered field, we obtain the distribution of the out-of-plane near-field component of the mode. When s-polarized scattered field is detected, we map the strongly confined in-plane fields propagating inside the gap. With decreasing gap width, we experimentally confirm the predicted reduction of mode diameter Dm, wavelength λm, and propagation length Lm. For TLs with 25 nm gap width we experimentally verify λm = 5.1 μm mode wavelength and Dm = 42 nm mode diameter (λ0/220). The propagation length is about Lm = 8.3 μm, which is more than 2 orders of magnitude larger than the mode diameter; ...

Optical activity and circular dichroism are fascinating physical phenomena originating from the interaction of light with chiral molecules or other nano objects lacking mirror symmetries in three-dimensional (3D) space. While chiral optical properties are weak in most of naturally occurring materials, they can be engineered and significantly enhanced in synthetic optical media known as chiral metamaterials, where the spatial symmetry of their building blocks is broken on a nanoscale. Although originally discovered in 3D structures, circular dichroism can also emerge in a two-dimensional (2D) metasurface. The origin of the resulting circular dichroism is rather subtle, and is related to non-radiative (Ohmic) dissipation of the constituent metamolecules. Because such dissipation occurs on a nanoscale, this effect has never been experimentally probed and visualized. Using a suite of recently developed nanoscale-measurement tools, we establish that the circular dichroism in a nanostructured metasurface occurs due to handedness-dependent Ohmic heating., The effect of Ohmic dissipation in two-dimensional chiral materials has never been experimentally verified. Here, Khanikaev et al. demonstrate that the circular dichroism in a nanostructured metasurface occurs due to handedness-dependent Ohmic heating.

Chiral antennas and metasurfaces can be designed to react differently to left- and right-handed circularly polarized light, which enables novel optical properties such as giant optical activity and negative refraction. Here, we demonstrate that the underlying chiral near-field distributions can be directly mapped with scattering-type scanning near-field optical microscopy employing circularly polarized illumination. We apply our technique to visualize, for the first time, the circular-polarization selective nanofocusing of infrared light in Archimedean spiral antennas, and explain this chiral optical effect by directional launching of traveling waves in analogy to antenna theory. Moreover, we near-field image single-layer rosette and asymmetric dipole–monopole metasurfaces and find negligible and strong chiral optical near-field contrast, respectively. Our technique paves the way for near-field characterization of optical chirality in metal nanostructures, which will be essential for the future development of chiral antennas and metasurfaces and their applications., The authors acknowledge support by the European Union through ERC starting grants (TERATOMO Grant 258461); the Spanish Ministry of Economy and Competitiveness (National Projects MAT2012-36580, MAT2012-37638, and FIS2013-41184P) and from the Basque Government (Project PI2011-1 and project ETORTEK nanogune’14). G.S. acknowledges support by the Office of Naval Research (Grant N00014-13-1-0837).

We demonstrate numerical refocusing in confocal microscopy. Our method is based on the recording of complex confocal data with synthetic optical holography, a recently introduced holographic modality for quantitative phase imaging, and the application of the pseudoinverse of the forward operator and a subsequent re-imaging to the new focal plane.

We present synthetic optical holography (SOH) as a new phase imaging modality in confocal microscopy, where amplitude and phase information are encoded holographically by a reference wave with a linear-in-time phase function. The implementation of SOH is technically simple, only requiring the addition of a linearly moving reference mirror. We demonstrate reliable confocal optical topography mapping with sub-nanometer depth resolution. Furthermore, we show numerical refocusing of out-of-focus confocal data, restoring a spatial resolution near the diffraction limit for situations where the sample is located up to 60 microns away from the system’s focal plane. We envision that quantitative phase imaging as provided by SOH will allow for a host of new possibilities in monochromatic confocal microscopy, ranging from stain- and dye-free confocal bio-imaging and phase-resolved second harmonic microscopy to three-dimensional imaging and computational aberration correction.

We present and demonstrate scattering-type near-field microscopy (s-SNOM) with circularly polarized illumination to map the chiral near-field distributions in metal nanostructures. We apply our technique to Archimedean spiral antennas and resolve circular polarization resolved nanofocusing of infrared light. Moreover, we near-field image single-layer chiral metasurfaces and connect the observed near-field response with circular dichroism in the far field. Our technique opens new ways of characterizing optical chirality in the near field of metal nanostructures which will be essential in the future development of chiral antennas and metasurfaces.

We study the propagation of mid-infrared surface plasmons on non-tapered and tapered two-wire transmission lines on Si and CaF2 substrates, the two materials representing substrates with large and small refractive index, respectively. A comparative numerical study predicts a larger effective wavelength and an increased propagation length (i.e. weaker damping) for the CaF2 substrate. By near-field microscopy we image the near-field distribution along the transmission lines and experimentally verify surface plasmon propagation. Amplitude- and phase-resolved near-field images of a non-tapered transmission line on CaF2 reveal a standing wave pattern caused by back-reflection of the surface plasmons at the open-ended transmission line. Calculated and experimental near-field images of tapered transmission lines on Si and CaF2 demonstrate that for both substrates the mid-IR surface plasmons are compressed when propagating along the taper. Importantly, the nanofocus at the taper apex yields a stronger local field enhancement for the low-refractive index substrate CaF2. We assign the more efficient nanofocusing on CaF2 to the weaker damping of the surface plasmons.

Using a tapered two-wire transmission line, researchers experimentally focus mid-infrared energy to a nanoscale confined spot with a diameter of 60 nm at the taper apex.

An unprecedented control of the spectral response of plasmonic nanoantennas has recently been achieved by designing structures that exhibit Fano resonances. This new insight is paving the way for a variety of applications, such as biochemical sensing and surface-enhanced Raman spectroscopy. Here we use scattering-type near-field optical microscopy to map the spatial field distribution of Fano modes in infrared plasmonic systems. We observe in real space the interference of narrow (dark) and broad (bright) plasmonic resonances, yielding intensity and phase toggling between different portions of the plasmonic metamolecules when either their geometric sizes or the illumination wavelength is varied. © 2011 American Chemical Society., P.A.-G, M.S., P.S., P.A., and R.H. acknowledge support from the European FP7 project “Nanoantenna” (FP7-HEALTH-F5-2009-241818-NANOANTENNA) and the National Project MAT2009-08393 from the Spanish Ministerio de Ciencia e Innovacion. M.S. and P.S. acknowledges financial support from “Programa de Formación de Personal Investigador” promoted by the Department of Education, Universities and Research of the Basque Government. P.N. and H.S. acknowledge support from the Robert A. Welch foundation (C-1222), the US Department of Defense NSEFF program (N00244-09-1-0067), and the Office of Naval Research (N00244-09-1-0989). C.W., N.A., A. K., and G.S. acknowledge support from the Office of Naval Research (N00014-10-1-0929) and the Air Force Research Laboratory.

4 páginas, 3 figuras.-- SpringerOpen., The electromagnetic interaction of light with polar materials shows a sharp and well defined electromagnetic response in the infrared (IR) region that consists mainly of excitation of optical phonons. Similar to surface plasmons in the visible region, surface phonons can couple efficiently to infrared light in micron-sized antennas made of polar materials. We applied the boundary element method to calculating the infrared electromagnetic response of single SiC disks acting as effective infrared antennas as a function of different parameters such as disk size and thickness. We also analyzed the effect of locating a probing metallic tip near the SiC disk to scatter light in the proximity of the SiC disk, thereby obtaining new spectral peaks connected with localized modes between the tip and the SiC disk. We then further investigated their application in IR scanning probe microscopy. A near-field map of the phononic resonances enhances the understanding of the nature of the IR extinction peaks.

5 páginas, 4 figuras.-- El pdf del artículo es la versión pre-print.-- et al., We describe transmission-mode scattering-type near-field optical microscopy (s-SNOM) with interferometric detection. Using this technique, we map the near-field modes of infrared antennas in both amplitude and phase. The use of dielectric probing tips, higher-harmonic demodulation, and a complex-valued subtraction of residual background yields accurate near-field images of the antenna modes. We map metallic nanorods, disks, and triangles, designed for antenna resonance at mid-infrared frequencies, in good agreement with numerical calculations of the modal field distribution. Furthermore, we show that transmission-mode s-SNOM can map the z-component of the antenna near fields. Our results establish a basis for future near-field characterization of complex antenna structures for molecular sensing and spectroscopy., Supported by the Etortek program of the Department of Industry of the Basque Government and the European FP7 project “Nanoantenna” (Health-F5-2009- 241818).

Optical and infrared antennas enable a variety of cutting-edge applications ranging from nanoscale photodetectors to highly sensitive biosensors. All these applications critically rely on the optical near-field interaction between the antenna and its ‘load’ (biomolecules or semiconductors). However, it is largely unexplored how antenna loading affects the near-field response. Here, we use scattering-type near-field microscopy to monitor the evolution of the near-field oscillations of infrared gap antennas progressively loaded with metallic bridges of varying size. Our results provide direct experimental evidence that the local near-field amplitude and phase can be controlled by antenna loading, in excellent agreement with numerical calculations. By modelling the antenna loads as nanocapacitors and nanoinductors, we show that the change of near-field patterns induced by the load can be understood within the framework of circuit theory. Targeted antenna loading provides an excellent means of engineering complex antenna configurations in coherent control applications, adaptive nano-optics and metamaterials., This research was supported by the Etortek program of the Department of Industry of the Basque Government and the Basque Foundation for Science (Ikerbasque). J.A. acknowledges CSIC special intramural project PIE 2008601039.

We demonstrate a method of rapidly acquiring background-free infrared near-field spectra by combining magnitude and phase resolved scattering-type scanning near-field optical microscopy (s-SNOM) with a wavelength-swept quantum cascade laser (QCL). Background-free measurement of both near-field magnitude and phase allows for direct comparison with far-field absorption spectra, making the technique particularly useful for rapid and straightforward nanoscale material identification. Our experimental setup is based on the commonly used pseudo-heterodyne detection scheme, which we modify by operating the interferometer in the white light position; we show this adjustment to be critical for measurement repeatability. As a proof-of-principle experiment we measure the near-field spectrum between 1690 and 1750 cm(-1) of a PMMA disc with a spectral resolution of 1.5 cm(-1). We finish by chemically identifying two fibers on a sample surface by gathering their spectra between 1570 and 1750 cm(-1), each with a measurement time of less than 2.5 minutes. Our method offers the possibility of performing both nanoscale-resolved point spectroscopy and monochromatic imaging with a single laser that is capable of wavelength-sweeping.

Phased-antenna metasurfaces can impart abrupt, spatially dependent changes to the amplitude, phase, and polarization of light and thus mold wavefronts in a desired fashion. Here we present an experimental and computational near-field study of metasurfaces based on near-resonant V-shaped antennas and connect their near- and far-field optical responses. We show that far fields can be obtained from limited, experimentally obtained knowledge of the near fields, paving the way for experimental near-field characterization of metasurfaces and other optical nanostructures and prediction of their far fields from the near-field measurements.

Background—Simvastatin, a 3-hydroxy-methylglutaryl coenzyme A reductase inhibitor, has been shown to lower serum cholesterol levels in clinical use. Moreover, statins exert beneficial effects in vascular diseases by inhibition of leukocyte rolling, adherence, and transmigration. The aim of this study was to determine if pretreatment with simvastatin attenuatesStaphylococcus aureusα-toxin–induced increase in leukocyte-endothelial interactions during exotoxemia.Methods and Results—The effects of simvastatin on leukocyte-endothelial cell interactions were observed by intravital microscopy in the rat mesenteric microcirculation. Simvastatin (50 or 100 μg/kg) was administered 18 hours before the study. Activation of microcirculation was induced by bolus administration of 40 μg/kgS aureusα-toxin. Exotoxemia resulted in a significant and time-dependent increase in leukocyte rolling, adherence, and transmigration of leukocytes as well as P-selectin expression on the intestinal vascular endothelium. Pretreatment with simvastatin significantly inhibited exotoxin-induced leukocyte rolling from 71±10 to 14±4.7 cells/min (PPPConclusions—These results demonstrate that simvastatin interferes with exotoxin-induced leukocyte-endothelial cell interactions, which may be relevant in various infectious diseases. Statin treatment may offer a new therapeutic strategy for these clinical conditions.

Holography has paved the way for phase imaging in a variety of wide-field techniques, including electron, X-ray and optical microscopy. In scanning optical microscopy, however, the serial fashion of image acquisition seems to challenge a direct implementation of traditional holography. Here we introduce synthetic optical holography (SOH) for quantitative phase-resolved imaging in scanning optical microscopy. It uniquely combines fast phase imaging, technical simplicity and simultaneous operation at visible and infrared frequencies with a single reference arm. We demonstrate SOH with a scattering-type scanning near-field optical microscope (s-SNOM) where it enables reliable quantitative phase-resolved near-field imaging with unprecedented speed. We apply these capabilities to nanoscale, non-invasive and rapid screening of grain boundaries in CVD-grown graphene, by recording 65 kilopixel near-field images in 26 s and 2.3 megapixel images in 13 min. Beyond s-SNOM, the SOH concept could boost the implementation of holography in other scanning imaging applications such as confocal microscopy., Holography provides amplitude and phase information when imaging objects, which enables greater understanding of a range of samples. Here, the authors adapt holography to scanning near-field optical microscopy, providing rapid phase-resolved imaging on the nanoscale at visible and infrared frequencies.

Methods and apparatus for imaging a phase or amplitude that characterizes a scattered field emanating from a physical medium. A local probe is stepped to a plurality of successive probe positions and illuminated with an illuminating beam, while a specified phase function is imposed on a reference beam relative to the illuminating beam. A field associated with the scattered field is superimposed with the reference beam and the detection of both yields a detected signal which is recorded as a function of probe position in order to obtain a hologram. The holograph is transformed, filtered, and retransformed to generate an image. Alternatively, the illuminating beam may directly illuminate successive positions of the physical medium.

Synthetic optical holography permits the use of arbitrary reference waves in digital holography, with each requiring an accompanying inversion algorithm. We consider, for example, a sinusoidal reference phase, resulting in an analog to pseudo-heterodyne interferometry.

A computer program for the analysis of high resolution Rutherford backscattering spectra (HR-RBS), which can be recorded with an electrostatic energy analyzer (ESA) and a resolution of about 1 keV, has been developed. The use of an ESA results in various differences compared to conventional RBS spectra, motivating the development of a new algorithm for simulation for these spectra. We present a Monte Carlo based diffusion-like fit approach for evaluation of the HR-RBS spectra, which is in particular useful for fitting concentration gradients. Examples for the application of the algorithm are shown to demonstrate its functionality.

We report the development of infrared-resonant antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as resonant antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent perspectives for optical nanoimaging and nanospectroscopy, pushing the detection and resolution limits in many applications, including nanoscale infrared mapping of organic, molecular, and biological materials, nanocomposites, or nanodevices.

We demonstrate a FTIR system that allows for infrared-spectroscopic nano-imaging with a thermal source (nano-FTIR). Based on super-focusing of thermal radiation with an infrared antenna and strong signal enhancement using an asymmetric FTIR spectrometer, we improve the spatial resolution of conventional IR spectroscopy by 2 orders of magnitude.

Fourier-transform infrared (FTIR) spectroscopy is a widely used analytical tool for chemical identification of inorganic, organic and biomedical materials, as well as for exploring conduction phenomena. Because of the diffraction limit, however, conventional FTIR cannot be applied for nanoscale imaging. Here we demonstrate a novel FTIR system that allows for infrared-spectroscopic nanoimaging of dielectric properties (nano-FTIR). Based on superfocusing of thermal radiation with an infrared antenna, detection of the scattered light, and strong signal enhancement employing an asymmetric FTIR spectrometer, we improve the spatial resolution of conventional infrared spectroscopy by more than two orders of magnitude. By mapping a semiconductor device, we demonstrate spectroscopic identification of silicon oxides and quantification of the free-carrier concentration in doped Si regions with a spatial resolution better than 100 nm. We envisage nano-FTIR becoming a powerful tool for chemical identification of nanomaterials, as well as for quantitative and contact-free measurement of the local free-carrier concentration and mobility in doped nanostructures.

5 páginas, 3 figuras., We demonstrate that the local near-field vector and polarization state on planar antenna structures and in nanoscale antenna gaps can be determined by scattering-type near-field optical microscopy (s-SNOM). The near-field vector is reconstructed from the amplitude and phase images of the in- and out-of-plane near-field components obtained by polarization-resolved interferometric detection. Experiments with a mid-infrared inverse bowtie antenna yield a vectorial near-field distribution with unprecedented resolution of about 10 nm and in excellent agreement with numerical simulations. Furthermore, we provide first direct experimental evidence that the nanoscale confined and strongly enhanced fields at the antenna gap are linearly polarized. s-SNOM vector-field mapping paves the way to a full near-field characterization of nanophotonic structures in the broad spectral range between visible and terahertz frequencies, which is essential for future development and quality control of metamaterials, optical sensors, and waveguides., Supported by the European FP7 project “Nanoantenna” (Health-F5-2009-241818) and the National Project MAT2009-08393 from the Spanish Ministerio de Ciencia e Innovacion. M.S. acknowledges financial support from “Programa de Formación de Personal Investigador” promoted by the Department of Education, Universities and Research of the Basque Government.

Der Kinofilm Habla con ella des spanischen Regisseurs Pedro Almodovar zeigt die Begegnung zweier Manner in einem Krankenhaus. Beide lieben jeweils eine Frau, die sich im Koma befindet. Fur den einen Mann ist die Auseinandersetzung mit einem im augenscheinlichen Langzeitschlaf befmdlichen Menschen ungewohnt und fremd, fur den andere Mann hingegen nicht mehr. Er ist im Umgang mit einer solchen Situation bereits erfahren und fordert den ersten Mann deshalb auf: Habla con elle/Sprich mit ihr! Er zeigt dabei auf die junge Frau, die nicht nur wahrend ihres kleinen Gespraches beinahe regungslos im Bett Hegt. Der Film stellt insgesamt die radikale Frage, ob ein Leben im Koma nicht eine Lebensform untefen anderen ist.