Optical techniques

Diagnosis of bile duct cancer often occur in advanced stages, leading to poor survival. Here, the authors combine light scattering and diffuse reflectance spectroscopies in a minimally invasive endoscopic technique for directly assessing the malignant potential of the bile duct lining, and demonstrate 97% detection accuracy.

The authors realize longitudinal deep-brain imaging through an intact mouse skull by constructing a high-speed reflection matrix microscope at 1.3 µm wavelength and developing a computational conjugate adaptive optics algorithm eliminating skull aberrations.

Here, the authors investigate the Raman spectra of few-layered WS₂ when the excitation energy is in resonance with the dark exciton, and observe a Fano resonance between dark excitonsand zone-edge acoustic phonons.

A 3D wide-field fluorescence microscopy method is introduced based on optical astigmatism combined with fluorescence source localization. It enables transcranial cortical microcirculation mapping in murine brain with high spatiotemporal resolution.

The authors present a planar photonic chip, which operate as a multiple-order analog spatial differentiator. It provides a route for designing fast, power-efficient, compact and low-cost devices used in edge detection and optical image processing, thus expanding the functions of standard microscopes.

The authors investigate whether strong light-matter coupling can alter the nonlinear optical response of molecules inside a microcavity. Focusing on electroabsorption as a model third order nonlinearity, they find that apparent discrepancies between experiment and classical transfer matrix modeling arise from dark states in the system and are not a sign of new physics in the strong coupling regime.

The authors present single-pixel imaging accelerated via swept aggregate patterns (SPI-ASAP), which combines a digital micromirror device with laser scanning for fast and reconfigurable pattern projection, and a lightweight reconstruction algorithm. They demonstrate real-time video streaming at 100 fps, and up to 12,000 fps offline.

Probing the localized electrocatalytic activity of heterogeneous electrocatalysts is crucial. Here, the authors propose a method of imaging the surface charge density and electrocatalytic activity of single two-dimensional electrocatalyst nanosheets.

The authors present a single-shot 3D imaging approach utilizing carefully designed point clouds projection based on a metasurface device. They show submillimeter depth accuracy and demonstrate the potential for hand gesture detection.

Structured Illumination Microscopy allows for the visualization of biological structures at resolutions below the diffraction limit, but this imaging modality is still hampered by high experimental complexity. Here, the authors present a combination of interferometry and machine learning to construct a structured illumination microscope for super resolution imaging of dynamic sub-cellular biological structures in multiple colors.

It is currently debated how to reliably distinguish liquid–liquid phase separation (LLPS) from other mechanisms. Here the authors report model-free calibrated half-FRAP (MOCHA-FRAP) to probe the barrier at the condensate interface that is responsible for preferential internal mixing in LLPS.

The authors introduce Bond-selective Intensity Diffraction Tomography, a computational mid-infrared photothermal microscopy technique based on a standard bright-field microscope and an add-on pulsed light source. It recovers both mid-infrared spectra and bond-selective 3D refractive index maps based on intensity-only measurements.

Super-resolution microscopy techniques can be challenging for live cells and thick samples. Here, the authors propose a method to reduce beam intensity and remove out-of-focus fluorescence background in image-scanning microscopy (ISM) and its combination with stimulated emission depletion (STED).

The authors developed an optical-fiber-based photoacoustic endoscope for gastroenterology. It can noninvasively view the internal vascular structures and visualize the hemodynamic response in a lesion.

The authors developed an open-source, low-cost, multi-channel time-tagging module for fluorescence lifetime image scanning microscopy and correlation spectroscopy that can tag in parallel multiple single-photon events with 30 ps precision.

Traditional methods for cell stiffness measurements are limited by long processing times and unsuitability for multiple cell analysis. Here, the authors demonstrate a fast technique based on acoustic stimulation and holographic imaging to reconstruct whole-cell stiffness maps of individual and multiple cells.

Holography recreates both the amplitude and wave front of a three dimensional object, meaning that the observer perceives the image in the nearly same way as they would the true object. Creating such holographic images is challenging computationally, and requires extremely fast display update. Here, the authors combine a fast memoryless computation algorithm with the ultra-rapid writing based on all-optical switching of a ferrimagnetic film.

Vibrational strong coupling (VSC) promises ultrasensitive IR spectroscopy and modification of material properties. Here, nanoscale mapping of VSC between organic molecules and individual IR nanoresonators is achieved by remote near-field spectroscopy.

Experimental evidence is given that upon the optical excitation of surface plasmon polaritons, a nonthermal electron population appears in the topmost domain of the plasmonic film directly coupled to the local fields.

The authors introduce an active-mode optical microcavity sensor with enhanced sensitivity via Förster resonant energy transfer. Changes in lasing wavelengths of both donor and acceptor enable quantitative molecular analysis and real-time monitoring of intracellular molecules.

The authors report high-efficiency emission depletion through a surface migration emission depletion mechanism, which takes advantage of the effects of surface quenching and energy migration in nanocrystals. They demonstrate super-resolution microscopy with very low depletion saturation intensities.

The authors demonstrate a label-free superresolution imaging method by using a hyperbolic material as a substrate for tailored light-matter interactions. The hyperbolic material enhanced scattering, combined with dark-field detection, result in 5.5-fold resolution improvement beyond the diffraction limit.

The optoelectronic performance of lead halide perovskite in highfluence applications are hindered by heterogeneous multi-polaron interactions in the nanoscale. Here, Nishda et al. spatially resolve sub-ns relaxation dynamics on the nanometer scale by ultrafast infrared pumpprobe nanoimaging.

Designing and manufacturing eco/bioresorbable electronic systems remains a challenge. The authors introduce a picosecond-pulsed laser-based scheme that exploits controlled patterning, thinning, and/or cutting to manipulate multilayers of eco/bioresorbable materials for a wide range of advanced electronic systems.

The authors developed a pristine hyperspectral SPR microscopy that enables monochromatic and polychromatic SPR imaging with flexible field-of-view option, single-pixel spectral SPR sensing and 2D quantification of thin films with resonant wavelength images.

Fiber-based micro-endoscopes are minimally invasive, but 3D imaging is limited by the need for bulky optical elements or rigid fibers. Here, the authors demonstrate holographic imaging through flexible and dynamically bent multi-core fibers by adding partially reflecting mirror to the distal fiber-tip.

Energy transfer between the electromagnetic field and atoms or molecules is fundamentally interesting. Here the authors demonstrate stepwise energy transfer between broadband mid-infrared optical pulses and vibrating methylsulfonylmethane molecules in aqueous solution.

Fabrication of metasurfaces with nanoscale structures is inefficient for large areas. Here, the authors introduce patterned pulse laser lithography for creating structured arrays with sub-wavelength feature on large-area thin films under ambient conditions.

Imaging though strongly scattering media is challenging and computationally intensive. Here, the authors show that tracking of moving objects can be achieved with minimal computational effort by combining cross-correlations of the measured speckle pattern at different times.

Mimicking human vision with metasurfaces, the authors propose a new paradigm for high field of view and ultrafast LiDAR, achieving performances also relevant for the next generation of imaging system for ADAS and robotic systems.

Sensitivity to noise is currently an obstacle to the use of quantum imaging techniques in real-world scenarios. Here, exploiting non-local cancellation of dispersion on time-frequency entangled photons, the authors show a 43dB improvement in resilience to noise for imaging protocols towards a quantum LiDAR.

The defocusing problem has been considered the main bottleneck for developing optoelectronic μ-compound eye (CE) cameras. Here, the authors report miniature optoelectronic CE cameras with an ommatidia logarithmic-profile. The camera enables large field-of-view imaging, spatial position identification, and sensitive trajectory monitoring of moving targets.

The authors present an approach to underwater imaging, which does not require tethering or batteries. The low-power camera uses power from harvested acoustic energy and communicates colour images wirelessly via acoustic backscatter.

Estimating the angular separation between two incoherent sources below the diffraction limit is challenging. Hypothesis testing and quantum state discrimination techniques are used to super-resolve sources of different brightness with a simple optical interferometer.

Here, the authors realize an ultra-high fluence X-ray laser by high-gain multilayer focusing optics. This enables in-solution imaging with 2-nm resolution in a single-pulse exposure, making strides toward biomolecular imaging under physiological conditions.

Studying microorganisms at high temperatures is challenging on conventional optical microscopes. Here, the authors introduce the concept of microscale laser heating over the full field of view by using gold nanoparticles as light absorbers, and study thermophile species up to 80 °C.

Optical binding enables light-induced assembly of many particles within a focus area. Here, the authors demonstrate that optical binding can occur outside the irradiated area by scattered light interacting with the particles outside the focus, generating arc-shape potential wells for particle trapping.

The authors introduce differentially enhanced compressed ultrafast photography, a phase imaging platform that combines high speed and sensitivity. They visualise propagation of passive current flows along myelinated axons, and electromagnetic pulses in lithium niobate.

Laser probing of integrated circuits using sub-bandgap photon energies remains a challenge. Here, the authors propose a super-resolution method capable of achieving probe placement accuracy to better than 10 nm; extraction of electro-optic waveforms from a node of a group of transistors and applied this to isolate and identify a fault on a defective device.

Light sheet microscopes reduce phototoxicity and background while improving imaging speed compared to widefield and confocal microscopes. Here the authors quantify the differences between Gaussian and lattice light sheets using simulations and experimental data in fixed and live cells.

Nanoscale emitters are useful for measuring biomolecular interactions, but are limited by weak signals. Here, the authors use a photonic crystal surface for 3000-fold signal enhancement, achieving single emitter sensitivity with extended on-time, and demonstrate its application in miRNA biomarker sensing.

Lensless fibre endoscopes are minimally invasive, but are often rigid and require calibration and fluorescence labelling. Here, the authors present a flexible endoscope based on a bare fibre bundle and a lensless Fourier holographic imaging configuration to detect weak reflections from unstained biological tissues.

There is a need to control molecular activities at high spatial precision. Here the authors report a real-time precision opto-control technology that detects a chemical-specific optical response from molecular targets, and precisely control photoswitchable microtubule polymerization inhibitors in cells.

Here, the authors develop a UV-compatible photonic integrated circuit for structured illumination microscopy on a conventional wide-field microscope. Operating at a wavelength of 360 nm, they generate switchable far-field fringe patterns, and demonstrate autofluorescence imaging of yeast cells.

The authors fabricate a 3D achromatic diffractive metalens on the end face of a single-mode fiber, useful for endoscopic applications. They demonstrate achromatic and polarization insensitive focusing across the entire near-infrared telecommunication wavelength band ranging from 1.25 to 1.65 µm.

The authors demonstrate an approach for imaging moving objects through a tortuous corridor filled with a random media. Their reduced spatial- and ensemble-speckle intensity correlation method allows for reconstruction of centimeter-sized hidden object with sub-millimeter resolution.

Diagnosis of gastric cancer currently requires gastroscopic biopsy, which requires time and expertize to perform. Here, the authors demonstrate a femto-SRS imaging method which showed high accuracy in diagnosing gastric cancer without the need for pathologistbased diagnosis.

Here, the authors demonstrate a blind and sparse near-field array signal processing approach to enhance the measurement quality of fibre-optic distributed acoustic sensors. It further enables the accurate estimation of the spatial coordinates of acoustic sources.

Infrared spectroscopy with plasmonic nanoantennas is limited by small overlap between molecules and hot spots, and sharp resonance peaks. The authors demonstrate spectral multiplexing of hook nanoantennas with gradient dimensions as ultrasensitive vibrational probes in a continuous ultra-broadband region and utilize machine learning for enhanced sensing performance.