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We report on experimental observation of unidirectional propagation of zero-momentum magnons in synthetic antiferromagnet consisting of strained CoFeB/Ru/CoFeB trilayer. Inherent non-reciprocity of spin waves in synthetic antiferromagnets with uniaxial anisotropy results in smooth and monotonous dispersion relation around Gamma point, where the direction of the phase velocity is reversed, while the group velocity direction is conserved. The experimental observation of this phenomenon by intensity-, phase-, and time-resolved Brillouin light scattering microscopy is corroborated by analytical models and micromagnetic simulations. [ABSTRACT FROM AUTHOR]

The transmission interference fringe (TIF) technique was developed to visualize the dynamics of evaporating droplets based on the Reflection Interference Fringe (RIF) technique for micro-sized droplets. The geometric formulation was conducted to determine the contact angle (CA) and height of macro-sized droplets without the need for the prism used in RIF. The TIF characteristics were analyzed through experiments and simulations to demonstrate a wider range of contact angles from 0 to 90°, in contrast to RIF's limited range of 0–30°. TIF was utilized to visualize the dynamic evaporation of droplets in the constant contact radius (CCR) mode, observing the droplet profile change from convex-only to convex-concave at the end of dry-out from the interference fringe formation. The TIF also observed the contact angle increase from the fringe radius increase. This observation is uniquely reported as the interference fringe (IF) technique can detect the formation of interference fringe between the reflection from the center convex profile and the reflection from the edge concave profile on the far-field screen. Unlike general microscopy techniques, TIF can detect far-field interference fringes as it focuses beyond the droplet-substrate interface. The formation of the convex-concave profile during CCR evaporation is believed to be influenced by the non-uniform evaporative flux along the droplet surface. [ABSTRACT FROM AUTHOR]

This paper presents a microscopy technique that can perform snapshot depth resolved optical imaging in the same manner as A-scan in ultrasound imaging and optical coherence tomography. In this technique, a laser line along the axial dimension is used to illuminate a sample to create a fluorescent line object. By transforming the line object along the axial dimension (Z) to a ring image on the lateral dimensions (X-Y) using a full cone mirror, common optics can be used to relay and acquire the ring image precisely. Then, by converting half of the ring image back to a line image using a half cone mirror, the opening side of the half cone mirror allows the line image, which contains the full depth resolved information of the line object, to be taken in one snapshot. This eliminates the requirement of axial scanning in traditional depth resolved imaging techniques such as confocal microscopy to obtain the same information. The technique is demonstrated by imaging fluorescent microspheres of different diameters. This technique offers a simple alternative to traditional depth resolved imaging techniques such as confocal microscopy and light sheet microscopy. It is particularly useful in imaging samples with multiple layers in which multiple A-scans or a few B-scans are sufficient to represent the entire sample. [ABSTRACT FROM AUTHOR]

Recent advancements in optical, terahertz, and microwave systems have unveiled non-transverse optical toroidal pulses characterized by skyrmionic topologies, fractal-like singularities, space-time nonseparability, and anapole-exciting ability. Despite this, the longitudinally polarized fields of canonical toroidal pulses notably lag behind their transverse counterparts in magnitude. Interestingly, although mushroom-cloud-like toroidal vortices with strong longitudinal fields are common in nature, they remain unexplored in the realm of electromagnetics. Here, we present strongly longitudinally polarized toroidal pulses (SLPTPs), which boast a longitudinal component amplitude exceeding that of the transverse component by over tenfold. This unique polarization property endows SLPTPs with robust propagation characteristics, showcasing nondiffracting behavior. The propagation-invariant strongly longitudinally polarized field holds promise for pioneering light–matter interactions, far-field superresolution microscopy, and high-capacity wireless communication utilizing three polarizations. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging allows to collect both spatial and quasi-continuous spectral information of an object. This work shows the innovative combination of single-pixel microscopy with hyperspectral imaging. An affordable hyperspectral microscope is able to observe micrometer-scale features of inorganic and biological samples and to reconstruct their spectral distribution with a high accuracy (i.e., a spatial and a spectral resolution of 9.0 μm and of 2.1 nm in the visible range, respectively). Furthermore, a statistical algorithm enables the identification of spectral responses of the targeted features as well as their classification. [ABSTRACT FROM AUTHOR]

Waveguide-based total internal reflection fluorescence microscopy has been widely adopted due to its excellent signal-to-noise ratio over a large field of view. However, with the increasing demand for label-free imaging, waveguide-based evanescent light scattering microscopy (ESM) has also garnered significant attention. Here, we present a low-cost waveguide-based microscope slide that offers easier integration with conventional optical microscopy. This microscope slide uses an incoherent light source coupled to a lithium tantalate (LT) planar waveguide to generate an evanescent light that illuminates samples located within a few hundred nanometers of the waveguide surface. We perform its application for imaging chromium nanoholes and polystyrene nanospheres, demonstrating its label-free, high-resolution, high-contrast imaging performance. LT waveguide microscope slides provide a simple and effective solution for ESM. [ABSTRACT FROM AUTHOR]

Strain imaging is a critical aspect in the design and characterization of opto-electronics, microelectronics, flexible electronics, and on-chip photonics. However, strain mapping techniques are often material specific and strain measurements in amorphous materials remain a challenge. Here, we demonstrate strain mapping and optical characterization of an amorphous semiconductor using scanning reflectance anisotropy microscopy. Using reflection anisotropy spectroscopy and finite element simulations on evaporated amorphous germanium films, we showcase the strain sensitivity of the ellipsometric parameters. We demonstrate nondestructive mapping for simple and complex strain states in amorphous systems. The sub-degree phase and amplitude sensitivity of the microscope is able to determine strain states on the order of 10 − 3 . [ABSTRACT FROM AUTHOR]

Endoscopy, enabling high-resolution imaging of deep tissues and internal organs, plays an important role in basic research and clinical practice. Recent advances in photoacoustic microscopy (PAM), demonstrating excellent capabilities in high-resolution functional imaging, have sparked significant interest in its integration into the field of endoscopy. However, there are challenges in achieving functional PAM in the endoscopic setting. This Perspective article discusses current progress in the development of endoscopic PAM and the challenges related to functional measurements. Then, it points out potential directions to advance endoscopic PAM for functional imaging by leveraging fiber optics, microfabrication, optical engineering, and computational approaches. Finally, it highlights emerging opportunities for functional endoscopic PAM in basic and translational biomedicine. [ABSTRACT FROM AUTHOR]

We present a compact laser system for quantitative two-photon excitation spectra measurements and ratiometric two-photon imaging of fluorescent protein indicators. The fundamental of the system is a short segment of photonic crystal fiber (PCF), which supports a nonlinear transformation of low-power ultrashort pulses by preserving temporal coherence, and this generates an ultrafast almost octave-spanning supercontinuum (SC). Accurate sculpting of the SC by its amplitude and phase modulation provides implementation of the spectroscopic and microscopic modalities. The spectroscopic one was exhibited by two-photon action cross section spectra measuring for the genetically encoded fluorescent sensing proteins of the vital biochemical parameters: acidity (SypHer3s), concentration of hydrogen peroxide (HyPer3 and HyPer7), redox status of NADH and glutathione (RexYFP and Grx1-roGFP2), hypohalous acids and their derivatives (Hypocrates). For the microscopy, we investigated and optimized the intensity pump pulse profiles under the high numerical objective by dispersion scan technique. We conducted real-time monitoring of the dynamics of hydrogen peroxide in HeLa cells with subcellular spatial resolution by means of ratiometric two-photon imaging of Hyper7 sensors. The presented hybrid laser system provides an ideal optical toolbox in order to develop ratiometric fluorescent sensors, which can be visualized in vivo using two-photon microscopy. [ABSTRACT FROM AUTHOR]

The requirements of augmented signal contrast provided by nanoparticle tags in biosensor microscopy-based point-of-care technologies for cancer and infectious disease diagnostics can be addressed through metallo-dielectric nanoarchitectures that enhance optical scattering and absorption to provide digital resolution detection of single tags with simple instrumentation. Photonic Resonator Interferometric Scattering Microscopy (PRISM) enables label-free visualization of nanometer-scale analytes such as extracellular vesicles and virions, and its applicability can be extended to biomolecular analyte counting through nanoparticle tags. Here, we present template-free, linker-less cryosoret nano-assemblies fabricated via adiabatic cooling (−196 °C) as plasmonic nano-antennas that provide high scattering contrast in PRISM. Plasmonic Ag and Au nanomaterials and their cryosorets are evaluated through imaging experiments and simulations based on the finite element method to understand the photo-plasmonic coupling effect at the surface of a photonic crystal (PC) interface. The Ag and Au cryosorets provide at most 8.29-fold and 6.77-fold higher signal contrast compared to their singlet counterpart. Through the simulations, the averaged field magnitude enhancements of 2.77-fold and 3.68-fold are observed for Ag and Au cryosorets when interfacing with PCs compared to bare glass substrates. The hybrid coupling between the localized Mie and delocalized Bragg plasmons of cryosorets and the underlying PC's guided mode resonance provides insights for developing nano-assembly-based nano-tags for biosensing applications. [ABSTRACT FROM AUTHOR]

We employed polarization-sensitive nonlinear optical microscopy to assess crystallinity of diamond microneedles. In the experiment, we mapped the coherent anti-Stokes Raman spectroscopy (CARS) signal in the vicinity of 1332 cm−1 diamond Raman peak over the needle length and demonstrated that the third-order nonlinear optical susceptibility remains the same at both micrometer-sized base and the nanoscale thin apex of the needle. This indicated the single-crystal nature of the diamond needle and allowed us to describe the results of the polarization CARS measurements in terms of the third-order nonlinear susceptibility of diamond. High crystallinity of the needle was also confirmed by measuring the linewidth of the zero-phonon line of the silicon-vacancy centers in diamond. [ABSTRACT FROM AUTHOR]

Quantifying the optical extinction cross section of a single plasmonic nanoparticle (NP) has recently emerged as a powerful method to characterize the NP morphometry, i.e., size and shape, with a precision comparable to electron microscopy while using a simple optical microscope. Here, we enhance the capabilities of extinction microscopy by introducing a high numerical aperture annular illumination coupled with a radial polarizer to generate a strong axial polarization component. This enables us to probe the NP response to axial polarized light, and, in turn, to distinguish flat-lying nanoplates from other geometries. Polarization-resolved optical extinction cross sections were acquired on 219 individual colloidal silver NPs of a nominally triangular nanoplate shape but, in practice, exhibiting heterogeneous morphometries, including decahedrons and non-plate spheroids. An unsupervised machine learning cluster analysis algorithm was developed, which allowed us to separate NPs into different groups, owing to the measured differences in cross sections. Comparison of the measurements with a computational model of the absorption and scattering cross section accounting for nanoplates of varying geometries beyond simple triangles provided insight into the NP shape of each group. The results provide a significant improvement of polarization-resolved optical extinction microscopy to reconstruct NP shapes, further boosting the utility of the method as an alternative to electron microscopy analysis. [ABSTRACT FROM AUTHOR]

With the discovery of two-dimensional (2D) ferroelectricity and ferromagnetism in van der Waals (vdW) materials, there has been significant interest in 2D multiferroics. Herein, we report the occurrence of weak ferromagnetism and magnetoelectricity in vdW antiferromagnet MnPSe3 single crystals. Our results demonstrate that MnPSe3 undergoes an antiferromagnetic transition at the Néel temperature TN = 70 K with weak ferromagnetism along the [1–10] direction. Detailed magnetoelectric (ME) data show that MnPSe3 exhibits a linear ME tensor αij with nine nonzero components. Additionally, a magnetically induced electric polarization as large as 98.5 μC/m2 is observed along the [110] direction, with a ME coefficient of 13.5 ps/m at 10 K for a magnetic field of 9 T applied along the [110] direction. Importantly, we discuss our experiments based on symmetry and microscopic analysis, thereby suggesting that the spin-dependent p-d hybridization mechanism plays an important role in the emergence of magnetic-field-induced ferroelectricity. Hence, our findings provide insights for exploring the ME coupling in vdW materials. [ABSTRACT FROM AUTHOR]

With the discovery of two-dimensional (2D) ferroelectricity and ferromagnetism in van der Waals (vdW) materials, there has been significant interest in 2D multiferroics. Herein, we report the occurrence of weak ferromagnetism and magnetoelectricity in vdW antiferromagnet MnPSe3 single crystals. Our results demonstrate that MnPSe3 undergoes an antiferromagnetic transition at the Néel temperature TN = 70 K with weak ferromagnetism along the [1–10] direction. Detailed magnetoelectric (ME) data show that MnPSe3 exhibits a linear ME tensor αij with nine nonzero components. Additionally, a magnetically induced electric polarization as large as 98.5 μC/m2 is observed along the [110] direction, with a ME coefficient of 13.5 ps/m at 10 K for a magnetic field of 9 T applied along the [110] direction. Importantly, we discuss our experiments based on symmetry and microscopic analysis, thereby suggesting that the spin-dependent p-d hybridization mechanism plays an important role in the emergence of magnetic-field-induced ferroelectricity. Hence, our findings provide insights for exploring the ME coupling in vdW materials. [ABSTRACT FROM AUTHOR]

Visualization and analysis of microstructure of materials or tissue play a pivotal role in industrial manufacturing and pathological diagnosis. Microwave-induced thermoacoustic microscopy (TAM) enables imaging at the microscopic level. TAM, however, is currently qualitative and cannot quantitatively measure intrinsic electromagnetic parameters of materials/tissue, such as conductivity. Here, we propose a quantitative microwave-induced thermoacoustic microscopy (qTAM) approach capable of quantitatively recovering conductivity using a finite element-based iterative inversion strategy coupled with thermoacoustic measurements. We validate the qTAM approach using tissue-mimicking phantoms, and demonstrate its applications to imaging flexible circuits, ex vivo rabbit bone, and rat brain tissues. The results obtained suggest that qTAM may have the potential to become a quantitative tool for microscopic imaging of materials and tissues. [ABSTRACT FROM AUTHOR]

Spin-wave computing, a potential successor to CMOS-based technologies, relies on the efficient manipulation of spin waves for information processing. While basic logic devices such as magnon transistors, gates, and adders have been experimentally demonstrated, the challenge for complex magnonic circuits lies in steering spin waves through sharp turns. In this study, we demonstrate with micromagnetic simulations and Brillouin light scattering microscopy experiments, that dipolar spin waves can propagate through 90° turns without distortion. The key lies in carefully designed in-plane magnetization landscapes, addressing challenges posed by anisotropic dispersion. The experimental realization of the required magnetization landscape is enabled by spatial manipulation of the uniaxial anisotropy using corrugated magnonic waveguides. The findings presented in this work should be considered in any magnonic circuit design dealing with anisotropic dispersion and spin wave turns. [ABSTRACT FROM AUTHOR]

Traditional single-pixel imaging (SPI) encounters challenges such as high sampling redundancy and poor imaging quality, constraining its widespread application. Despite a range of orthogonal modulation modes have been employed in structured illumination to enhance imaging performance, some encoding issues still persist in information sampling, impeding the further progression of SPI. We propose an SPI method based on orthogonal Hermite–Gaussian (HG) moments, achieving improved imaging reconstruction through differential modulation of HG basis patterns and linear weighting of acquired intensity. Both simulations and experiments confirm superior imaging quality and computation efficiency of proposed Hermite–Gaussian single-pixel imaging (HG-SI), especially at low-measurement levels. Moreover, we incorporate compressed sensing algorithms within the framework of HG-SI, integrating moments-based sampling strategies to optimize imaging capability under sparse measurements. Our research underscores the effectiveness of HG modulation in SPI reconstruction, enabling high-quality outcomes via compressed sampling. This advancement propels the investigation of optical field modulation modes within SPI and holds promise in offering a universal solution for weak-intensity and non-visible light microscopy. [ABSTRACT FROM AUTHOR]

We present temporal compressive holographic microscopy to achieve high-speed phase imaging with a low-speed camera. In this method, alternating deep denoising network and total variation denoiser are combined into a plug-and-play framework to reconstruct ten high-speed holographic frames from a single-shot measurement. Therefore, we can observe a 500 frame per second (fps) holographic scene when the camera works at 50 fps. This technique provides an effective tool to detect dynamic phase change scenes. [ABSTRACT FROM AUTHOR]

Visualizing micro- and nano-scale biological entities requires high-resolution imaging and is conventionally achieved via optical microscopic techniques. Optical diffraction limits their resolution to ∼200 nm. This limit can be overcome by using ions with ∼1 MeV energy. Such ions penetrate through several micrometers in tissues, and their much shorter de Broglie wavelengths indicate that these ion beams can be focused to much shorter scales and hence can potentially facilitate higher resolution as compared to the optical techniques. Proton microscopy with ∼1 MeV protons has been shown to have reasonable inherent contrast between sub-cellular organelles. However, being a transmission-based modality, it is unsuitable for in vivo studies and cannot facilitate three-dimensional imaging from a single raster scan. Here, we propose proton-induced acoustic microscopy (PrAM), a technique based on pulsed proton irradiation and proton-induced acoustic signal collection. This technique is capable of label-free, super-resolution, 3D imaging with a single raster scan. Converting radiation energy into ultrasound enables PrAM with reflection mode detection, making it suitable for in vivo imaging and probing deeper than proton scanning transmission ion microscopy (STIM). Using a proton STIM image of HeLa cells, a coupled Monte Carlo+k-wave simulations-based feasibility study has been performed to demonstrate the capabilities of PrAM. We demonstrate that sub-50 nm lateral (depending upon the beam size and energy) and sub-micron axial resolution (based on acoustic detection bandwidth and proton beam pulse width) can be obtained using the proposed modality. By enabling visualization of biological phenomena at cellular and subcellular levels, this high-resolution microscopic technique enhances understanding of intricate cellular processes. [ABSTRACT FROM AUTHOR]

The effect of lattice relaxation instability (martensitic transition) on piezoelectric fields (EPE) in spontaneously ordered GaInP2/GaAs epitaxial layers was demonstrated using scanning Kelvin probe microscopy in combination with electron microscopy and optical spectroscopy measurements. The transition manifests itself in the dependence of the surface potential of the epi-layer on the mechanical (cleavage) and thermal (annealing) impacts. This is associated with a switching of the crystal lattice between relaxed and strained martensitic states, corresponding to a change in EPE in the epi-layer. The measured surface potential values (0.2–2.4 V) correspond to EPE within ±100 kV/cm and a strong decrease in |EPE| with increasing layer thickness, indicating the pinning of the Fermi level and piezoelectric doping. Our results open up the prospects for using spontaneously ordered semiconductor alloys to control electronic states in semiconductor nanostructures by controlling their piezoelectric fields. [ABSTRACT FROM AUTHOR]

Herein, a facile, catalyst-free, and dry topochemical transformation strategy for transforming the Bi2S3 nanowires to the Bi2Se3 nanowires, which has been realized through an atmospheric pressure high-temperature selenization treatment, has been developed. The complete topochemical transformation has been verified by combining x-ray diffraction, Raman spectroscopy, energy dispersive spectrometer, x-ray photoelectron spectroscopy, transmission electron microscopy, and selected area electron diffraction measurements. Systematical optical characterizations, including polarization-resolved optical microscopy images and polarization-dependent Raman spectra, have revealed the strong anisotropy of the Bi2Se3 nanowires. Furthermore, finite-different time-domain simulations have consolidated that the Bi2Se3 nanowires possess highly anisotropic absorption cross sections across the ultraviolet to far infrared spectral range, laying a solid foundation for the realization of ultra-broadband polarized optoelectronic applications. On the whole, this pioneering study depicts a unique avenue for topological material design accompanied with the integration of additional functionalities beyond the intrinsic counterparts, opening up an attractive research field for polarized photonics and optoelectronics. [ABSTRACT FROM AUTHOR]

This article explores the advancements and applications of optical microscopy in the field of biology. It discusses various studies that have pushed the boundaries of what is possible with optical microscopy, including the use of nonlinear micro-spectroscopy techniques, artificial intelligence and deep learning algorithms, and structured illumination microscopy. The article also discusses the use of optical microscopy in ecotoxicology for detecting metallic nanoparticles in organisms and the development of correlative multimodal imaging techniques. It highlights improvements in signal-to-background ratios achieved through different imaging methods in pseudotumor and tumor models, as well as the use of light-sheet fluorescence microscopy for high-speed 3D imaging. The article also mentions advancements in structured illumination microscopy for super-resolution imaging and the translation of optical coherence tomography images into H&E-like stained images for improved interpretability. It concludes by discussing the potential of correlative super-resolution microscopy in merging different imaging techniques to achieve higher resolution and a deeper understanding of biological systems. [Extracted from the article]

Brillouin microscopy, an emerging mechanical imaging technology, has made rapid development in recent years. The Brillouin imaging signal is not only determined by acoustic waves in the optical focus volume but also by acoustic waves outside the focus volume. Here, we study how acoustic propagation across the polydimethylsiloxane (PDMS)–ethanol interface affects the heterodyne impulsive stimulated Brillouin scattering (ISBS) signal. When the acoustic direction is perpendicular to the interface, a frequency component corresponding to the PDMS Brillouin shift appears in the signal although the probe focus is in the ethanol. The transmitted wave from PDMS appears when the acoustic wave propagates to the probe focus. To discuss the acoustic contribution of spatial resolution and the acoustic mode propagation distance, it is necessary to consider the acoustic properties of the medium. The influence of transmitted waves on the interference signal is observed in about 100 μm (phonon mean free path in ethanol). Since ISBS analyzes the signal in the time domain, it is possible to distinguish the transmitted wave from the local signal in a single pixel. Different spatial resolutions are obtained by the time-domain method and frequency-domain method. Using mechanical information outside the optical focus volume, ISBS has the potential to image with fewer pixels, which is more flexible and faster than point-by-point scanning. [ABSTRACT FROM AUTHOR]

Polarization-resolved second harmonic generation (P-SHG) microscopy is commonly used to analyze the second-order susceptibility, χ(2), tensor, which enables the calculation of the molecular structure of harmonophores. However, despite extensive research on type I collagen, the measured χ(2) ratios vary considerably among published values, which raises the question of whether P-SHG imaging is universally applicable to all tissues containing harmonophores. In this work, we propose that the deviation of χ(2) ratios is primarily due to ignoring the molecular tilt angle and chirality in image analysis. To confirm our hypothesis, we present an analytical model based on C6 symmetry that takes into account these two factors. We also introduce an imaging scheme that splits SHG into X- and Y-polarized image components for χ(2) tensor analysis. Our approach effectively improves the precision of determining χ(2) ratios, depending on how much the two factors affect the P-SHG signals. [ABSTRACT FROM AUTHOR]

In this work, we report a pixel reassignment based super-resolution reconstruction algorithm for structured illumination microscopy (entitled PR-SIM). PR-SIM provides a twofold theoretical resolution enhancement by reassigning the pixels in raw SIM images with respect to the center of each illumination fringe and applying further deconvolution. By comparing with frequency domain based algorithms, PR-SIM is more immune to fringe distortion and, hence, it is more suited for large-field SIM in that it processes the raw images locally. Meanwhile, the reconstruction speed of PR-SIM can be enhanced by skipping empty regions in the image and further enhanced by employing GPU-base parallel calculation. Overall, we can envisage that the PR-SIM can be extended for other illumination modulation based microscopic techniques. [ABSTRACT FROM AUTHOR]

Phase-shift droplets provide a flexible and dynamic platform for therapeutic and diagnostic applications of ultrasound. The spatiotemporal response of phase-shift droplets to focused ultrasound, via the mechanism termed acoustic droplet vaporization (ADV), can generate a range of bioeffects. Although ADV has been used widely in theranostic applications, ADV-induced bioeffects are understudied. Here, we integrated ultra-high-speed microscopy, confocal microscopy, and focused ultrasound for real-time visualization of ADV-induced mechanics and sonoporation in fibrin-based, tissue-mimicking hydrogels. Three monodispersed phase-shift droplets—containing perfluoropentane (PFP), perfluorohexane (PFH), or perfluorooctane (PFO)—with an average radius of ∼6 μm were studied. Fibroblasts and tracer particles, co-encapsulated within the hydrogel, were used to quantify sonoporation and mechanics resulting from ADV, respectively. The maximum radial expansion, expansion velocity, induced strain, and displacement of tracer particles were significantly higher in fibrin gels containing PFP droplets compared to PFH or PFO. Additionally, cell membrane permeabilization significantly depended on the distance between the droplet and cell (d), decreasing rapidly with increasing d. Significant membrane permeabilization occurred when d was smaller than the maximum radius of expansion. Both ultra-high-speed and confocal images indicate a hyper-local region of influence by an ADV bubble, which correlated inversely with the bulk boiling point of the phase-shift droplets. The findings provide insight into developing optimal approaches for therapeutic applications of ADV. [ABSTRACT FROM AUTHOR]

The article discusses the use of optical spectroscopy and microscopy for characterizing materials with high spatial resolution. It explains the limitations of traditional techniques due to the diffraction of light and introduces the concept of near-field imaging using metallic scanning probe tips. The article highlights the advantages of this approach, such as improved sensitivity, higher spatial resolution, and a broader wavelength range. It also explores the various applications of near-field imaging, including nano-FTIR, tip-enhanced Raman scattering, and photo-induced force microscopy. The article concludes by discussing the future directions of the field, such as multimodal imaging and computational imaging techniques. [Extracted from the article]

Optical tweezers are ideal tools for cell manipulation in vivo due to their non-contact trapping ability. In the current studies, the optical trapping of cells can only be achieved in light-permeable organs. It is important to expand the application of optical tweezers to opaque tissues and organs, where biological activities are the primary focus of biomedical research. However, the optical manipulation of cells in these opaque organs cannot be imaged using a conventional transillumination microscope due to the opacity of these organs. Here, we use optical tweezers to trap erythrocytes and measure the cell deformability in mouse liver, which are imaged with oblique back-illumination microscopy (OBM). In the microscope system, two fibers are fixed at the same oblique angle on both sides of the microscopic objective, illuminating the trapping target asymmetrically. The dual-wavelength OBM strategy allows for obtaining a differential phase contrast image in a single-shot by color channel separation. The OBM can image the flowing and trapped erythrocytes in vivo in real-time. Furthermore, the erythrocyte deformability in vivo is evaluated with optical tweezers. The spring stiffness in vivo is 8.2 ± 2.1 μN m−1, which is obtained by stretching the trapped cells with blood drag flow. Our works make it possible to utilize optical tweezers to study the live cell dynamics in opaque organs, which will expand the application of optical tweezers in the fields of biomechanical studies. [ABSTRACT FROM AUTHOR]

Photoacoustic microscopy with high spatial resolution and fast imaging acquisition allows observing dynamic processes of optical absorption-based microanatomic structures in three dimensions. An evanescent sensor accesses ultrasonic detection with high sensitivity and broad bandwidth while suffering from limited field of view (FOV), thus compromising the photoacoustic imaging acquisition rate. Here, we develop an optical-scanning evanescent sensor by fast deflection of the interrogation light along the interface of prism and water using a one-dimensional galvanometer, demonstrating excellent detection sensitivity of ∼132 Pa with a broadband frequency response of >140-MHz at an enlarged FOV of ∼2.90 × 0.19 mm2. Incorporating the optical-scanning evanescent sensor in photoacoustic microscopy, a volumetric image (∼3.0 × 0.25 × 1.0 mm3) with micrometer-scale spatial resolution is acquired within ∼2.5 s by synergistically scanning both photoacoustic illumination laser and sensor's interrogation light. High-speed imaging of flowing microparticles within a capillary tube offers the visualizations of the traveling processes in three dimensions. Potentially, the optical-scanning evanescent sensor allows photoacoustic microscopy accommodating to dynamic imaging at cellular level such as in vivo flow cytometry of circulating tumor cells. [ABSTRACT FROM AUTHOR]

We study theoretically and experimentally the process of Brillouin light scattering on an array of silicon disks on a thin Permalloy layer. We show that phase-resolved Brillouin light scattering microscopy performed on an array of weakly interacting dielectric nanoresonators can detect nanoscale waves and measure their dispersion. In our experiment, we were able to map the evolution of the phase of the spin wave with a wavelength of 204 nm and a precision of 6 nm. These results demonstrate the feasibility of all-optical phase-resolved characterization of nanoscale spin waves. [ABSTRACT FROM AUTHOR]

Microsphere-assisted microscopy is a sub-diffraction-limited imaging technique, which uses dielectric microspheres to collect the near-field information of an object. In this work, the bulk of the classical microsphere-based system is reduced by the simple introduction of a ball lens. The miniaturized imaging system has been designed and vertically assembled. Performance of the proposed dual-sphere system is quantified through numerical simulations and experiments. A theoretical impulse response with a full width at half maximum smaller than half of the wavelength is reached in air. As a proof of concept, 500-nm-period standard gratings and gold nanoparticles are observed without a classical objective, validating a sub-wavelength resolution with a high imaging quality and low aberrations over the field of view. [ABSTRACT FROM AUTHOR]

The ability to detect small metallic nanoparticles by optical microscopy inside environmentally relevant species may have a wide impact for ecotoxicology studies. Here, we demonstrate four-wave mixing microscopy on individual small gold nanoparticles inside the hepatopancreas of Oniscus Asellus, a terrestrial isopod, which ingests metals found in the soil. After the exposure to food containing 10 nm radius gold nanoparticles, hepatopancreas tubules were collected, and nanoparticles were imaged by four-wave mixing microscopy with high contrast, locating them with sub-cellular resolution in the volume, despite the significant light scattering from these multi-cellular organs. Notably, the ultrafast dynamics of the four-wave-mixing non-linearity of gold nanoparticles resonantly excited and probed at their localized surface plasmon allows them to be distinguished from other metal deposits in the hepatopancreas, which manifest as a long-lived photothermal contrast. Our findings bring unexpected insight into the location of gold nanoparticles in relation to the cell types forming the hepatopancreas. Considering its simplicity, volumetric imaging capabilities, specificity, and compatibility with living cell studies, four-wave mixing microscopy holds great potential to investigate the fate of metal nanoparticles inside biological systems. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) microscopy is emerging as a promising approach for mechanical imaging in biological settings. It is based on a spectroscopic backscattering SBS setup, but with scanning of the sample and using higher apertures of the excitation and collection optics for adequate spatial sampling. Here, we provide direct experimental measurements and theoretical predictions of the aperture-induced spectral effects of SBS microscopy in water—a key constituent of biological systems. It is shown that with increasing numerical aperture (NA), the Brillouin frequency shift and peak gain decrease, while the Brillouin linewidth broadens asymmetrically with the commencing of an extended tail in the low frequency region for NA > ∼0.5. Further, significant distortions of the Brillouin spectral line shape are predicted for NAs close to 1, affecting the ability to retrieve spectral parameters of the Brillouin medium precisely and accurately. [ABSTRACT FROM AUTHOR]

Correlative multimodal imaging is a useful approach to investigate complex structural relations in life sciences across multiple scales. For these experiments, sample preparation workflows that are compatible with multiple imaging techniques must be established. In one such implementation, a fluorescently labeled region of interest in a biological soft tissue sample can be imaged with light microscopy before staining the specimen with heavy metals, enabling follow-up higher resolution structural imaging at the targeted location, bringing context where it is required. Alternatively, or in addition to fluorescence imaging, other microscopy methods, such as synchrotron x-ray computed tomography with propagation-based phase contrast or serial blockface scanning electron microscopy, might also be applied. When combining imaging techniques across scales, it is common that a volumetric region of interest (ROI) needs to be carved from the total sample volume before high resolution imaging with a subsequent technique can be performed. In these situations, the overall success of the correlative workflow depends on the precise targeting of the ROI and the trimming of the sample down to a suitable dimension and geometry for downstream imaging. Here, we showcase the utility of a femtosecond laser (fs laser) device to prepare microscopic samples (1) of an optimized geometry for synchrotron x-ray tomography as well as (2) for volume electron microscopy applications and compatible with correlative multimodal imaging workflows that link both imaging modalities. [ABSTRACT FROM AUTHOR]

In recent years, image-scanning microscopy (ISM, also termed pixel-reassignment microscopy) has emerged as a technique that improves the resolution and signal-to-noise compared to confocal and widefield microscopy by employing a detector array at the image plane of a confocal laser scanning microscope. Here, we present a k-space analysis of coherent ISM, showing that ISM is equivalent to spotlight synthetic-aperture radar and analogous to oblique-illumination microscopy. This insight indicates that ISM can be performed with a single detector placed in the k-space of the sample, which we numerically demonstrate. [ABSTRACT FROM AUTHOR]

A recently developed technique of transmission-mode microwave impedance microscopy (T-MIM) has greatly extended the capabilities of standard reflection-mode MIM to novel applications, such as the in operando study of nanoscale electro-acoustic devices. As is common for new techniques, systematic design principles for boosting sensitivity and balancing bandwidth are lacking. Here, we show numerically and analytically that the T-MIM signal is proportional to the reflection-mode voltage enhancement factor η of the circuit, as long as the output impedance of the local voltage source is properly treated. We show that this proportionality holds in the currently achievable "weak sampling" regime and beyond, for which we demonstrate a realistic path with commercially available superconducting components and critically coupled impedance matching networks. We demonstrate that for these next-generation designs, the sensitivity is generally maximized at a slightly different frequency from the unloaded S11 resonance, which can be explained by the maximum power transfer theorem. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenide based 2D/2D or 2D/3D van der Waals heterostructures exhibit superior properties for high-performance electronics, tunneling transistors, and catalysts. Here, we report on the fabrication of high quality 2D/3D MoS2/MoO2 heterostructures with an atomic clean interface by one-step chemical vapor deposition. Optical microscopy, atomic force microscopy, Raman spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy measurements reveal the high-quality of as-grown samples and the specific epitaxial relationship between MoS2 and MoO2: MoS2[ 1 ¯ 1 ¯ 20]//MoO2[001] and MoS2[ 1 ¯ 100]//MoO2[201]. Photoluminescence and Kelvin probe force microscopy measurements combined with density functional theory calculations confirm the interfacial charge transfer from MoS2 to the underlying MoO2. Furthermore, MoO2 induced in-plane anisotropy in MoS2 was revealed using angle-resolved polarized Raman and photoluminescence spectroscopy with anisotropic ratios of 1.27 (Raman) and 1.29 (photoluminescence), respectively, which is most possibly attributed to anisotropic interfacial charge interactions. Our findings provide an excellent platform for the investigation on interfacial effects. Moreover, the in-plane anisotropy in MoS2 induced by MoO2 has expanded the application of isotropic MoS2 in the polarization-dependent fields. [ABSTRACT FROM AUTHOR]

We demonstrate a method that permits wavefront aberration correction using an array of electrowetting prisms. A fixed high fill factor microlens array followed by a lower fill factor adaptive electrowetting prism array is used to correct wavefront aberration. The design and simulation of such aberration correction mechanism is described. Our results show significant improvement to the Strehl ratio by using our aberration correction scheme which results in diffraction limited performance. Compactness and effectiveness of our design can be implemented in many applications that require aberration correction, such as microscopy and consumer electronics. [ABSTRACT FROM AUTHOR]

The increasing demand for lithium-ion batteries (LIBs) continuously stimulates the research community to seek advanced fabrication of anodes with improved performance and lifespan. Silicon (Si), as one of the most promising anode materials, has been the main focus of both research and industry. In this paper, we report a type of Si alloy anode for LIBs manufactured by the supersonic cold spray technique. The microscopic analysis revealed the uniform morphologies of the anodes, indicating that Si and other metal particles were well bonded. Specific discharge capacities were obtained for the cold-sprayed anodes by half-coin cell tests, with the highest value of 1047 mAh g−1 at a current rate of 0.05 C. Most importantly, the energy-dispersive x-ray spectroscopy results demonstrated none oxidation of the powders after the cold spray process. The results strongly indicate that the concept of using cold spray technique to fabricate Si alloy anode is feasible. Compared to the conventional methods of fabricating Si anodes, the cold spray approach is simple, convenient, and scalable. This method may revolutionarily change the LIBs industries. [ABSTRACT FROM AUTHOR]

Off-axis interferometric modules built on an ordinary bright field microscope make it possible to achieve single-shot quantitative phase imaging (QPI) by adding sufficient spatial carrier into the interferograms. However, compared with its on-axis counterparts, imaging configurations for off-axis interferometric modules have several disadvantages regarding optical aberration, stability, and space-bandwidth utilization of the lenses system. Herein, by demultiplexing technology based on polarization gratings, we propose a single-shot spatial light interference microscopy named as polarization-multiplexing light interference microscopy (PLIM) with on-axis imaging configuration to realize single-shot QPI. Although the imaging system is on-axis, the PLIM system still can generate sufficient spatial carrier, so we can adjust the orientation and absolute value of the spatial carrier independently of the magnification ratio of the imaging system. The experimental results prove that the PLIM system has better temporal phase stability compared with conventional grating-based QPI technologies and is suitable for high resolution QPI. [ABSTRACT FROM AUTHOR]

Imaging of transparent samples such as cells is important in the biomedicine field; however, insignificant absorption and weakly scattering limit the imaging contrast of phase objects. Here, we propose and demonstrate Brewster differential microscopy based on simple optical reflection at the glass interface. The combination of spin–orbit interaction of light and the Brewster effect can perform two-dimensional differentiation to the incident light distribution and, thus, achieves isotropic edge-enhanced imaging of pure phase objects, which overcomes the limitation of traditional one-dimensional imaging. Furthermore, by introducing bias retardation, we also reconstruct the original phase distribution. The proposed microscopic imaging mechanism does not involve any complex modulation devices and takes advantages of simple and low-cost structure. The results indicate that our research shows promising applications for nondestructive imaging of biological cells. [ABSTRACT FROM AUTHOR]

Surgery represents the mainstream therapeutic modality in oncology. Aggressive radical surgery to achieve no residual tumor would improve survival, which is mainly affected by vascular involvement and accuracy of judging the negative margin of tumor resection. However, there is currently no intraoperative tool that can simultaneously perform microscopic analysis of the peritumoral vasculature in vivo and the surgical margin pathology of the tumor ex vivo, which leads to the randomness of one-time complete resection of the tumor, and the patient may have to undergo secondary surgery. To address this critical need, we developed a 532/266 nm dual-wavelength photoacoustic (PA) microscopy imaging (532/266-PAI) system that enables both in vivo tumor regional vascular involvement analysis and pathological margin assessment of fresh ex vivo tumor samples. A mammary tumor animal model was established to mimic the process of tumor resection, from in vivo imaging vascular involvement of tumor to intraoperative judgment of negative tumor margins. It is proved that the 532/266-PAI technology can identify the tumor vascular involvement through vascular visualization, determine the surgical plan, and then judge whether the tumor is completely removed through ultraviolet PA (UPA) tumor pathological imaging. Re-excision and secondary margin evaluation are performed when margin positive is diagnosed in the intraoperation UPA imaging. The 266/532-PAI technique has great potential for complete tumor resection in surgical navigation. [ABSTRACT FROM AUTHOR]

Interest in the piezoelectric and ferroelectric properties of micro- and nanomaterials is increasing due to the advances being made in nanotechnology. However, there are only a few techniques that can detect functional properties at the nanoscale, and one of them is piezo-response force microscopy (PFM). So far, this technique has been mainly used to study surface properties of piezoelectric films. In this investigation, we develop a procedure to study films in the cross section by PFM and to investigate the relaxor-ferroelectric domain structure of pristine, screen-printed, and aerosol-deposited 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 films in the cross section. Due to the different preparation methods used for two films, the grain size and, thus, the relaxor-ferroelectric domain structures differ. Micron-scale domains are observed in the screen-printed films, while sub micrometer-scale domains are found in the aerosol-deposited films. However, no change in the ferroelectric domain structures was observed across the thicknesses of the films. [ABSTRACT FROM AUTHOR]

The generation of vector beams with complex spatial distributions is significant in the field of optical manipulation, optical metrology, optical microscopy, and so on. In this work, we propose a method to generate arbitrary vector beams, which is based on the complex amplitude beam shaping technology and the interferometric optical path configuration. With the method, we can achieve pixel-level control of amplitude, phase, and polarization of an arbitrary vector beam. Furthermore, different polarization states and orientations can be designed to coexist in one beam. The method has been verified with theoretical analysis and experimental results. The proposed method expands the application range of vector beams and provides a conducive way to explore the optical properties of the vector beams. [ABSTRACT FROM AUTHOR]

Light-sheet microscopes must compromise among field of view, optical sectioning, resolution, and detection efficiency. High-numerical-aperture (NA) detection objective lenses provide higher resolution, but their narrow depth of field inefficiently captures the fluorescence signal generated throughout the thickness of the illumination light sheet when imaging large volumes. Here, we present ExD-SPIM (extended depth-of-field selective-plane illumination microscopy), an improved light-sheet microscopy strategy that solves this limitation by extending the depth of field (DOF) of high-NA detection objectives to match the thickness of the illumination light sheet. This extension of the DOF uses a phase mask to axially stretch the point-spread function of the objective lens while largely preserving lateral resolution. This matching of the detection DOF to the illumination-sheet thickness increases the total fluorescence collection, reduces the background, and improves the overall signal-to-noise ratio (SNR), as shown by numerical simulations, imaging of bead phantoms, and imaging living animals. In comparison to conventional light sheet imaging with low-NA detection that yields equivalent DOF, the results show that ExD-SPIM increases the SNR by more than threefold and dramatically reduces the rate of photobleaching. Compared to conventional high-NA detection, ExD-SPIM improves the signal sensitivity and volumetric coverage of whole-brain activity imaging, increasing the number of detected neurons by over a third. [ABSTRACT FROM AUTHOR]

Structured illumination microscopy (SIM), with the advantages of full-field imaging and low photo-damage, is one of the most well-established fluorescence super-resolution microscopy techniques that raised great interest in biological sciences. However, conventional SIM techniques generally require at least nine images for image reconstruction, and the quality of super-resolution significantly depends on high-accuracy illumination parameter estimation, which is usually computationally intense and time-consuming. To address these issues, we propose a robust seven-frame SIM reconstruction algorithm with accelerated correlation-enabled parameter estimation. First, a modulation-assigned spatial filter is employed to remove unreliable backgrounds associated with low signal-to-noise ratios. Then, we propose a coarse-to-fine accelerated correlation algorithm to eliminate the redundant iterations of the traditional correlation-based scheme. The frame reduction is achieved by a specially designed phase-shifting strategy combined with pixel-wise fluorescence pre-calibration. We experimentally demonstrate that, compared with conventional iterative correlation-based methods, the proposed algorithm improves the computational efficiency by a factor of 4.5 while maintaining high accuracy illumination parameter estimation. Meanwhile, our method achieves high-quality super-resolution reconstruction even with a reduction in two raw images, which improves the efficiency of image acquisition and ensures the robustness toward complex experimental environments. [ABSTRACT FROM AUTHOR]

As superconducting quantum processors increase in complexity, techniques to overcome constraints on frequency crowding are needed. The recently developed method of laser-annealing provides an effective post-fabrication method to adjust the frequency of superconducting qubits. Here, we present an automated laser-annealing apparatus based on conventional microscopy components and demonstrate preservation of highly coherent transmons. In addition, we perform noise spectroscopy to investigate the change in defect features, in particular, two-level system defects, after laser-annealing. Finally, we present a local heating model as well as demonstrate aging stability for laser-annealing on the wafer scale. Our work constitutes an important step toward both understanding the underlying physical mechanism and scaling up laser-annealing of superconducting qubits. [ABSTRACT FROM AUTHOR]

Microwave impedance microscopy (MIM) is an emerging scanning probe technique that measures the local complex dielectric function using near-field microwave. Although it has made significant impacts in diverse fields, a systematic, quantitative understanding of the signal's dependence on various important design parameters is lacking. Here, we show that for a wide range of MIM implementations, given a complex tip-sample admittance change Δ Y , the MIM signal—the amplified change in the reflected microwave amplitude—is − G · Δ Y / 2 Y 0 · η 2 · V in , where η is the ratio of the microwave voltage at the probe to the incident microwave amplitude, Y0 is the system admittance, and G is the total voltage gain. For linear circuits, η is determined by the circuit design and does not depend on V in . We show that the maximum achievable signal for different designs scales with η 2 or η when limited by input power or sample perturbation, respectively. This universal scaling provides guidance on diverse design goals, including maximizing narrow-band signal for imaging and balancing bandwidth and signal strength for spectroscopy. [ABSTRACT FROM AUTHOR]

Quantum imaging is an ever expanding research field in which the aim is to exploit the quantum nature of light to enhance image reconstruction capabilities. Despite a number of successful demonstrations for quantum imaging, quantum microscopy still seems out of the range for practical applications due to different physical and technical reasons. Here, we propose an imaging method exploiting the quantum correlations of photon pairs and a scanning microscope to achieve fast, single mode quantum imaging. We first test our technique on a metal grating to estimate the resolution capabilities of our system. Moreover, we assess its potential in terms of the number of available independent pixels at full resolution compared to different quantum imaging approaches. Finally, we demonstrate scanning quantum microscopy of onion epithelial cells, paving the way toward scalable quantum microscopy for bio-physical applications. Our results, combined with the rapidly evolving photon-pair generation and detection technology toward the mid-infrared, could lead to an extension of quantum microscopy applications toward the mid-infrared to access the molecular fingerprint region. [ABSTRACT FROM AUTHOR]

Laser-based amorphization on the back surface of a 525-μm thick crystalline silicon sample is studied. To deposit sufficient energy for a local change from a crystalline to an amorphous state, laser irradiation at 2-μm wavelength with 25-ps pulse duration is combined with Bessel beam shaping. Deterministic single-site modifications and homogeneous continuous lines of amorphous silicon are demonstrated. Optical and electron microscopy together with Raman spectroscopy measurements highlight the material transformations featuring the formation of subwavelength periodic surface structures. The investigations open up possibilities for processing in-built microelectronic devices. [ABSTRACT FROM AUTHOR]