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Augmented and virtual reality devices are being actively investigated and implemented for a wide range of medical uses. However, significant gaps in the evaluation of these medical devices and applications hinder their regulatory evaluation. Addressing these gaps is critical to demonstrating the devices’ safety and effectiveness. We outline the key technical and clinical evaluation challenges discussed during the US Food and Drug Administration’s public workshop, “Medical Extended Reality: Toward Best Evaluation Practices for Virtual and Augmented Reality in Medicine” and future directions for evaluation method development. Evaluation challenges were categorized into several key technical and clinical areas. Finally, we highlight current efforts in the standards communities and illustrate connections between the evaluation challenges and the intended uses of the medical extended reality (MXR) devices. Participants concluded that additional research is needed to assess the safety and effectiveness of MXR devices across the use cases.

We present an experimental method that utilizes a conic probe attached to an integrating sphere for characterizing the small-spot luminance of virtual reality (VR) head-mounted displays (HMDs). This allows for the measurement of relative luminance in virtual scenes and the assessment of VR displays for visualizing grayscale medical images. We characterized the relative luminance of the VIVE Pro and Oculus Rift by displaying test patterns with a circular dark spot of varying diameter in the bright field and compared the probe performance with commercially available systems. Compared to a conventional flat-panel display, the results show a significant level of veiling glare in the HMDs using both a customized conic probe with improved optical performance and an advanced imaging photometer. We also found no significant change in the relative luminance response with the probe’s working distance for the HMDs due to their unique optical architecture for near-eye viewing conditions. Our results highlight the issue of high veiling glare in HMDs and the importance of small-spot luminance measurements to adequately evaluate the technical performance of HMDs for emerging medical applications.

Virtual reality (VR) head mounted displays (HMDs) require both high spatial resolution and fast temporal response. However, methods to quantify the VR image quality in the spatiotemporal domain when motion exists are not yet standardized. In this study, we characterize the spatiotemporal capabilities of three VR devices: the HTC VIVE, VIVE Pro, and VIVE Pro 2 during smooth pursuit. A spatiotemporal model for VR HMDs is presented using measured spatial and temporal characteristics. Among the three evaluated headsets, the VIVE Pro 2 improves the display temporal performance using a fast 120 Hz refresh rate and pulsed emission with a small duty cycle of 5%. In combination with a high pixel resolution beyond 2 k $$\times$$ × 2 k per eye, the VIVE Pro 2 achieves an improved spatiotemporal performance compared to the VIVE and VIVE Pro in the high spatial frequency range above 8 cycles per degree during smooth pursuit. The result demonstrates that reducing the display emission duty cycle to less than 20% is beneficial to mitigate motion blur in VR HMDs. Frame rate reduction (e.g., to below 60 Hz) of the input signal compared to the display refresh rate of 120 Hz yields replicated shadow images that can affect the image quality under motion. This work supports the regulatory science research efforts in development of testing methods to characterize the spatiotemporal performance of VR devices for medical use.

Cross-platform development of medical applications in extended-reality (XR) head-mounted displays (HMDs) often relies on game engines with rendering capabilities currently not standardized in the context of medical visualizations. Many aspects of the visualization pipeline including the characterization of color have yet to be consistently defined across rendering models and platforms. We examined the transfer of color properties from digital objects, through the rendering and image processing steps, to the RGB values sent to the display device. Five rendering pipeline configurations within the Unity engine were evaluated using 24 digital color patches. In the second experiment, the same configurations were evaluated with a tissue slide sample image. Measurements of the change in color associated with each configuration were characterized using the CIE 1976 color difference ( $${\Delta}{\text{E}}$$ ). We found that the distribution of $${\Delta}{\text{E}}$$ for the first experiment ranges from zero, as in the case using an Unlit Shader, to 25.97, as in the case using default configurations. The default Unity configuration consistently returned the highest $${\Delta}{\text{E}}$$ across all 24 colors and also the largest range of color differences. In the second experiment, $${\Delta}{\text{E}}$$ E ranged from 7.49 to 34.18. The Unlit configuration resulted in the highest $${\Delta}{\text{E}}$$ in three of four selected pixels in the tissue sample image. Changes in color image properties associated with texture import settings were then evaluated in a third experiment using the TG18-QC test pattern. Differences in pixel values were found in all nine of the investigated texture import settings. The findings provide an initial characterization of color transfer and a basis for future work on standardization, consistency, and optimization of color in medical XR applications.

Potential commercial applications for transition metal dichalcogenide (TMD) semiconductors such as MoS(2) rely on unique material properties that are only accessible at monolayer to few-layer thickness regimes. Therefore, production methods that lend themselves to scalable and controllable formation of TMD films on surfaces are desirable for high volume manufacturing of devices based on these materials. We have developed a new thermal atomic layer deposition (ALD) process using bis(tert-butylimido)-bis(dimethylamido)molybdenum and 1-propanethiol to produce MoS(2)-containing amorphous films. We observe self-limiting reaction behavior with respect to both the Mo and S precursors at a substrate temperature of 350 °C. Film thickness scales linearly with precursor cycling, with growth per cycle values of (≈)0.1 nm/cycle. As-deposited films are smooth and contain nitrogen and carbon impurities attributed to poor ligand elimination from the Mo source. Upon high-temperature annealing, a large portion of the impurities are removed, and we obtain few-layer crystalline 2H-MoS(2) films.

The structural polymorphism in transition metal dichalcogenides (TMDs) provides exciting opportunities for developing advanced electronics. For example, MoTe(2) crystallizes in the 2H semiconducting phase at ambient temperature and pressure, but transitions into the 1T′ semimetallic phase at high temperatures. Alloying MoTe(2) with WTe(2) reduces the energy barrier between these two phases, while also allowing access to the T(d) Weyl semimetal phase. The Mo(1–x) W(x)Te(2) alloy system is therefore promising for developing phase change memory technology. However, achieving this goal necessitates a detailed understanding of the phase composition in the MoTe(2)-WTe(2) system. We combine polarization-resolved Raman spectroscopy with x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) to study bulk Mo(1–x)W(x)Te(2) alloys over the full compositional range x from 0 to 1. We identify Raman and XRD signatures characteristic of the 2H, 1T′, and T(d) structural phases that agree with density-functional theory (DFT) calculations, and use them to identify phase fields in the MoTe(2)–WTe(2) system, including single-phase 2H, 1T′, and T(d) regions, as well as a two-phase 1T′ + T(d) region. Disorder arising from compositional fluctuations in Mo(1–x)W(x)Te(2) alloys breaks inversion and translational symmetry, leading to the activation of an infrared 1T′-MoTe(2) mode and the enhancement of a double-resonance Raman process in 2H-Mo(1–x) W(x)Te(2) alloys. Compositional fluctuations limit the phonon correlation length, which we estimate by fitting the observed asymmetric Raman lineshapes with a phonon confinement model. These observations reveal the important role of disorder in Mo(1–x)W(x)Te(2) alloys, clarify the structural phase boundaries, and provide a foundation for future explorations of phase transitions and electronic phenomena in this system.

Visual information is a critical component in the evaluation and communication of patient medical information. As display technologies have evolved, the medical community has sought to take advantage of advances in wider color gamuts, greater display portability, and more immersive imagery. These image quality enhancements have shown improvements in the quality of healthcare through greater efficiency, higher diagnostic accuracy, added functionality, enhanced training, and better health records. However, the display technology advances typically introduce greater complexity in the image workflow and display evaluation. This paper highlights some of the optical measurement challenges created by these new display technologies and offers possible pathways to address them.

High-volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultrathin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor-phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metal–organic chemical vapor deposition (MOCVD) route for MoS2 film growth in a research-grade single-wafer reactor. Using bis(tert-butylimido)bis(dimethylamido)molybdenum and diethyl disulfide, we deposit MoS2 films from ∼1 nm to ∼25 nm in thickness on SiO2/Si substrates. We show that layered 2H-MoS2 can be produced at comparatively low reaction temperatures of 591 °C at short deposition times, approximately 90 s for few-layer films. In addition to the growth studies performed on SiO2/Si, films with wafer-...

We demonstrate a method for measuring the transverse chromatic aberration (TCA) in a virtual reality head-mounted display. The method relies on acquiring images of a digital bar pattern and measuring the displacement of different color bars. This procedure was used to characterize the TCAs in the Oculus Go, Oculus Rift, Samsung Gear, and HTC Vive. The results show noticeable TCAs for the Oculus devices for angles larger than 5° from the center of the field of view. TCA is less noticeable in the Vive in part due to off-axis monochromatic aberrations. Finally, user measurements were conducted, which were in excellent agreement with the laboratory results.

We study the crystal symmetry of few-layer 1T′ MoTe2 using the polarization dependence of the second harmonic generation (SHG) and Raman scattering. Bulk 1T′ MoTe2 is known to be inversion symmetric; however, we find that the inversion symmetry is broken for finite crystals with even numbers of layers, resulting in strong SHG comparable to other transition-metal dichalcogenides. Group theory analysis of the polarization dependence of the Raman signals allows for the definitive assignment of all the Raman modes in 1T′ MoTe2 and clears up a discrepancy in the literature. The Raman results were also compared with density functional theory simulations and are in excellent agreement with the layer-dependent variations of the Raman modes. The experimental measurements also determine the relationship between the crystal axes and the polarization dependence of the SHG and Raman scattering, which now allows the anisotropy of polarized SHG or Raman signal to independently determine the crystal orientation.

Fiber fracture is a major contributor for the initiation of failure in fiber-reinforced polymer composites. The purpose of this study was to identify where damage occurs when a fiber fractures in a composite. Because this dynamic event occurs in less than 100 1ns, obtaining experimental evidence has been prohibitively difficult. Here, we report a novel method using a model composite, comprised of a spirolactam-based mechanophore-functionalized epoxy resin with a single embedded glass fiber. The ductile epoxy matrix is loaded under tension, which transfers load through interfacial shearing to the embedded brittle fiber, causing the fiber to break into segments. Fluorescence lifetime imaging microscopy (FLIM) is used to visualize regions of mechanophore activation and quantify changes in the dye's local environment such as relaxations on the nanosecond timescale. FLIM of these single fiber fragmentation test (SFFT) samples reveals localized damage zones in the epoxy matrix, not only at the point of fiber fragmentation, but also at distances remote from the fracture site that extend radially into the matrix up to two fiber diameters. The average mechanophore lifetime in the bulk epoxy is (1.5 ± 0.5) ns and in the damage regions is (0.75 ± 0.15) ns. This new data reveals the existence of polymer matrix yielding, which occurs during the fiber fracture event, and agrees with a dynamic model that predicts yielding behavior in the matrix during fracture. These results suggest that the damage from fiber fracture is more extensive than previously recognized. This new approach can be used to elucidate damage in other mechanical tests. The subsequent insights into composite damage mechanisms promises to dramatically accelerate the development of tough, durable, and damage tolerant composites.

High volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultra-thin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metalorganic chemical vapor deposition (MOCVD) route for MoS2 film growth in a research-grade single-wafer reactor. Using bis(tert-butylimido)-bis(dimethylamido)molybdenum and diethyl disulfide we deposit MoS2 films from ≈ 1 nm to ≈ 25 nm in thickness on SiO2/Si substrates. We show that layered 2H-MoS2 can be produced at comparatively low reaction temperatures of 591 °C at short deposition times, approximately 90 s for few-layer films. In addition to the growth studies performed on SiO2/Si, films with wafer-level uniformity are demonstrated on 50 mm quartz wafers. Process chemistry and impurity incorporation from precursors are also discussed. This low-temperature and fast process highlights the opportunities presented by metalorganic reagents in the controlled synthesis of TMDs.

We demonstrate a multimodal superresolution microscopy technique based on a phase masked excitation beam in combination with spatially filtered detection. The theoretical foundation for calculating the focus from a non-paraxial beam with an arbitrary azimuthally symmetric phase mask is presented for linear and two-photon excitation processes as well as the theoretical resolution limitations. Experimentally this technique is demonstrated using two-photon luminescence from 80 nm gold particle as well as two-photon fluorescence lifetime imaging of fluorescent polystyrene beads. Finally to illustrate the versatility of this technique we acquire two-photon fluorescence lifetime, two-photon luminescence, and second harmonic images of a mixture of fluorescent molecules and 80 nm gold particles with

We introduce a simple criterion to identify two-dimensional (2D) materials based on the comparison between experimental lattice constants and lattice constants mainly obtained from Materials-Project (MP) density functional theory (DFT) calculation repository. Specifically, if the relative difference between the two lattice constants for a specific material is greater than or equal to 5%, we predict them to be good candidates for 2D materials. We have predicted at least 1356 such 2D materials. For all the systems satisfying our criterion, we manually create single layer systems and calculate their energetics, structural, electronic, and elastic properties for both the bulk and the single layer cases. Currently the database consists of 1012 bulk and 430 single layer materials, of which 371 systems are common to bulk and single layer. The rest of calculations are underway. To validate our criterion, we calculated the exfoliation energy of the suggested layered materials, and we found that in 88.9% of the cases the currently accepted criterion for exfoliation was satisfied. Also, using molybdenum telluride as a test case, we performed X-ray diffraction and Raman scattering experiments to benchmark our calculations and understand their applicability and limitations. The data is publicly available at the website http://www.ctcms.nist.gov/~knc6/JVASP.html.

Polymer composite materials are found throughout the world both natural and artificial in origin. In the vast majority of applications in these arenas, composites serve as structural support or reinforcement. Demand for lightweight tough composites is growing in multiple application spaces such as aerospace, biomaterials, and infrastructure with physical properties as diverse as the applications. The unifying component in all composites is the presence of the interphase. Many measurement techniques and measurement tools have been developed for the study of this crucial region in composite materials. Many of these methods are great for the measurement and study of bulk properties or model systems. However, development of tools that permit the direct observation of interactions at the interphase during applied stress are needed. Here we employ fluorescence lifetime imaging and hyperspectral imaging to observe activation of a fluorogenic dye at the composite interface as a result of applied stress. The advantages of this system include commercial availability of the dye precursor, and simple one-pot functionalization. The attachment of the dye at the interface is easily monitored through emission wavelength shifts or fluorescence lifetime. Interfacial mechano-responsive dyes have potential for both fundamental studies as well as industrial use as a structural health monitoring tool.

We present a new transfer procedure for graphene using acetic acid, which removes the residue that is common in standard acetone treatments. Post-transfer samples cleaned with acetic acid and acetone were characterized using Raman spectroscopy and atomic force microscopy for comparison. We further illustrate the quality of our transfer process by using fluorescence quenching to create an optical map of surface contaminants., 3 pages, 3 figures

Solid-state quantum emitters, such as artificially engineered quantum dots or naturally occurring defects in solids, are being investigated for applications ranging from quantum information science and optoelectronics to biomedical imaging. Recently, these same systems have also been studied from the perspective of nanoscale metrology. In this letter, we study the near-field optical properties of a diamond nanocrystal hosting a single nitrogen vacancy center. We find that the nitrogen vacancy center is a sensitive probe of the surrounding electromagnetic mode structure. We exploit this sensitivity to demonstrate nanoscale fluorescence lifetime imaging microscopy (FLIM) with a single nitrogen vacancy center by imaging the local density of states of an optical antenna.

We examine anharmonic contributions to the optical phonon modes in bulk $T_d$-MoTe$_2$ through temperature-dependent Raman spectroscopy. At temperatures ranging from 100 K to 200 K, we find that all modes redshift linearly with temperature in agreement with the Gr\"{u}neisen model. However, below 100 K we observe nonlinear temperature-dependent frequency shifts in some modes. We demonstrate that this anharmonic behavior is consistent with the decay of an optical phonon into multiple acoustic phonons. Furthermore, the highest frequency Raman modes show large changes in intensity and linewidth near $T\approx 250$ K that correlate well with the $T_d \to 1T^\prime$ structural phase transition. These results suggest that phonon-phonon interactions can dominate anharmonic contributions at low temperatures in bulk $T_d$-MoTe$_2$, an experimental regime that is currently receiving attention in efforts to understand Weyl semimetals., Comment: 14 pages, 3 figures, 1 table

With a template-stripping fabrication technique, we demonstrate the mass fabrication of high-quality, uniform, ultrasharp (10 nm) metallic probes suitable for single-molecule fluorescence imaging, tip-enhanced Raman spectroscopy (TERS), and other near-field imaging techniques. We achieve reproducible single-molecule imaging with sub-20-nm spatial resolution and an enhancement in the detected fluorescence signal of up to 200. Similar results are obtained for TERS imaging of carbon nanotubes. We show that the large apex angle (70.5°) of our pyramidal tip is well suited to scatter the near-field optical signal into the far-field, leading to larger emission enhancement and hence to a larger quantum yield. Each gold or silver pyramidal probe is used on-demand, one at a time, and the unused tips can be stored for extended times without degradation or contamination. The high yield (>95%), reproducibility, durability, and massively parallel fabrication (1.5 million identical probes over a wafer) of the probes hold promise for reliable optical sensing and detection and for cementing near-field optical imaging and spectroscopy as a routine characterization technique., ACS Nano, 6 (10), ISSN:1936-0851, ISSN:1936-086X

Potential commercial applications for transition metal dichalcogenide (TMD) semiconductors such as MoS2 rely on unique material properties that are only accessible at monolayer to few-layer thickness regimes. Therefore, production methods that lend themselves to the scalable and controllable formation of TMD films on surfaces are desirable for high volume manufacturing of devices based on these materials. The authors have developed a new thermal atomic layer deposition process using bis(tert-butylimido)-bis(dimethylamido)molybdenum and 1-propanethiol to produce MoS2-containing amorphous films. They observe a self-limiting reaction behavior with respect to both the Mo and S precursors at a substrate temperature of 350 °C. Film thickness scales linearly with precursor cycling, with growth per cycle values of ≈0.1 nm/cycle. As-deposited films are smooth and contain nitrogen and carbon impurities attributed to poor ligand elimination from the Mo source. Upon high-temperature annealing, a large portion of the impurities are removed, and the authors obtain few-layer crystalline 2H-MoS2 films.

Optical antennas made of gold nanoparticles are used to enhance the spectroscopic response of single molecules. With a scannable optical half-wave antenna in the form of a gold nanorod we achieve a spatial resolution of 20nm in fluorescence imaging. We explore simultaneous fluorescence and Raman enhancement of dye molecules in the junction of two gold nanoparticles and find similar enhancements as a function of interparticle distance for both fluorescence and Raman scattering. We compare our results with theoretical predictions and provide possible explanations.

We demonstrate a multimodal superresolution microscopy technique based on phase masked excitation and spatially filtered detection. We acquire two-photon fluorescent lifetime and second harmonic images of fluorophores mixed with gold particles with 100 nm resolution.

Metamaterials can negatively diffract optical-wavelength light; however, they suffer from high losses and only work over a narrow band of frequencies. Researchers now show how nonlinear optics in thin films of graphite can offer a solution. The negligible thickness of the layers reduces the losses, and the linear band structure of the material ensures broadband operation.

The structural polymorphism in transition metal dichalcogenides (TMDs) provides exciting opportunities for developing advanced electronics. For example, MoTe$_2$ crystallizes in the 2H semiconducting phase at ambient temperature and pressure, but transitions into the 1T$^\prime$ semimetallic phase at high temperatures. Alloying MoTe$_2$ with WTe$_2$ reduces the energy barrier between these two phases, while also allowing access to the T$_d$ Weyl semimetal phase. The MoWTe$_2$ alloy system is therefore promising for developing phase change memory technology. However, achieving this goal necessitates a detailed understanding of the phase composition in the MoTe$_2$-WTe$_2$ system. We combine polarization-resolved Raman spectroscopy with X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) to study MoWTe$_2$ alloys over the full compositional range x from 0 to 1. We identify Raman and XRD signatures characteristic of the 2H, 1T$^\prime$, and T$_d$ structural phases that agree with density-functional theory (DFT) calculations, and use them to identify phase fields in the MoTe$_2$-WTe$_2$ system, including single-phase 2H, 1T$^\prime$, and T$_d$ regions, as well as a two-phase 1T$^\prime$ + T$_d$ region. Disorder arising from compositional fluctuations in MoWTe$_2$ alloys breaks inversion and translational symmetry, leading to the activation of an infrared 1T$^\prime$-MoTe$_2$ mode and the enhancement of a double-resonance Raman process in 2H-MoWTe$_2$ alloys. Compositional fluctuations limit the phonon correlation length, which we estimate by fitting the observed asymmetric Raman lineshapes with a phonon confinement model. These observations reveal the important role of disorder in MoWTe$_2$ alloys, clarify the structural phase boundaries, and provide a foundation for future explorations of phase transitions and electronic phenomena in this system.

Inelastic light scattering in crystals has historically been treated as a spatially incoherent process, giving rise to incoherent optical radiation. Here we demonstrate that Raman scattering can be spatially coherent, in which case it depends on the dimensionality and symmetry of the scatterer. Using near-field spectroscopy, we measure a correlation length of $\ensuremath{\sim}30\text{ }\text{ }\mathrm{nm}$ for the optical phonons in graphene, the results varying with vibrational symmetries and spatial confinement of the phonons.

A theoretical study describing the coherence properties of near-field Raman scattering in two- and one-dimensional systems is presented. The model is applied to the Raman modes of pristine graphene and graphene edges. Our analysis is based on the tip-enhanced Raman scheme, in which a sharp metal tip located near the sample surface acts as a broadband optical antenna that transfers the information contained in the spatially correlated (but nonpropagating) near field to the far field. The dependence of the scattered signal on the tip-sample separation is explored, and the theory predicts that the signal enhancement depends on the particular symmetry of a vibrational mode. The model can be applied to extract the correlation length Lc of optical phonons from experimentally recorded near-field Raman measurements. The coherence properties of optical phonons have been broadly explored in the time and frequency domains, and the spatially resolved approach presented here provides a complementary methodology for the study of local material properties at the nanoscale., Physical Review X, 4 (3), ISSN:2160-3308

A theory describing the near-field Raman enhancement in two-dimensional (2D) systems is presented. The analysis quantifies the near-field Raman intensity as a function of the tip-sample distance, Raman polarizability tensor components, incident laser beam configuration, and tip orientation relative to the sample plane. Our results show that the near-field Raman intensity is inversely proportional to the 10th and 8th power of the tip-sample distance in the incoherent and coherent scattering regimes, respectively. Optimal conditions for the tip inclination angle for different configurations are determined, and the results can be used as a guide for tip-enhanced Raman spectroscopy (TERS) experiments in 2D systems such as graphene, two-dimensional electron gases, and topological insulators.

The development of optical metamaterials has resulted in the demonstration of remarkable physical properties, including cloaking, optical magnetism, and negative refraction. The latter has attracted particular interest, mainly because of its promise for super-resolution imaging. In recent years, negative refraction has been demonstrated with plasmonic materials and nonlinear discrete elements. However, the widespread use of negative refraction at optical frequencies is limited by high losses and strong dispersion effects, which typically limits operation to narrow frequency bands. Here we use degenerate four-wave mixing (d-4WM) to demonstrate controllable negative refraction at a graphene interface, which acts as a highly efficient phase-conjugating surface. The scheme has very low loss because of the very small thickness of the nonlinear material and it ensures broadband operation due to the linear bandstructure of graphene.

We developed a novel optical defocusing method for studying spatial coherence of photoexcited electrons and holes near edges of graphene. Our method is applied to measure the localization l(D) of the disorder-induced Raman D band (∼1350 cm(-1)) with a resolution of a few nanometers. Raman scattering experiments performed in a helium bath cryostat reveal that as temperature is decreased from 300 to 1.55 K, the length l(D) increases. We found that the localization of the D band varies as 1/T(1/2), giving strong evidence that l(D) scales with the coherence length of photoexcited electrons near graphene edges.

This paper reports the experimental determination of the phase-breaking length L of conduction electrons in graphene using Raman spectroscopy. Based on the double-resonance model, we extract L from the spatial dependence of the D band susceptibility near the graphene edge. By using prior knowledge of sample properties and the excitation point-spread function we are able to determine the spatial variation of the Raman susceptibilities with high accuracy, and the results reveal a phase-breaking length L~40nm near the graphene edge., 5 pages, 2 figures

We report the results of a new Rosenbluth measurement of the proton form factors at Q^2 values of 2.64, 3.20 and 4.10 GeV^2. Cross sections were determined by detecting the recoiling proton in contrast to previous measurements in which the scattered electron was detected. At each Q^2, relative cross sections were determined to better than 1%. The measurement focussed on the extraction of G_E/G_M which was determined to 4-8% and found to approximate form factor scaling, i.e. \mu_p G_E \approx G_M. These results are consistent with and much more precise than previous Rosenbluth extractions. However, they are inconsistent with recent polarization transfer measurements of comparable precision, implying a systematic difference between the two techniques., Comment: 5 pages, 3 figures, submitted to PRL

The continually increasing demands for higher-speed and lower-operating-power devices have resulted in the continued impetus to shrink photonic components. We demonstrate a primitive nanophotonic integrated circuit element composed of a single silver nanowire and single-layer molybdenum disulfide (MoS2) flake. Using scanning confocal fluorescence microscopy and spectroscopy, we find that nanowire plasmons can excite MoS2 photoluminescence and that MoS2 excitons can decay into nanowire plasmons. Finally, we show that the nanowire may serve the dual purpose of both exciting MoS2 photoluminescence via plasmons and recollecting the decaying exciton as nanowire plasmons. The potential for subwavelength light guiding and strong nanoscale light–matter interaction afforded by our device may facilitate compact and efficient on-chip optical processing.

We have developed interferometric systems to measure nanosize structures and freeze their motion in time. Researchers have also suggested a method to extract both phase and amplitude information for crystallography.

The detection and identification of nanoparticles is of growing interest in atmospheric monitoring, medicine, and semiconductor manufacturing. While elastic light scattering with interferometric detection provides good sensitivity to single particles, active optical components prevent scalability of realistic sizes for deployment in the field or clinic. Here, we report on a simple phase-sensitive nanoparticle detection scheme with no active optical elements. Two measurements are taken simultaneously, allowing the amplitude and phase to be decoupled. We demonstrate the detection of 25 nm Au particles in liquid in Δt ∼ 1 ms with a signal-to-noise ratio of ∼ 37. Such performance makes it possible to detect nanoscale contaminants or larger proteins in real time without the need of artificial labeling.