Science Daily September 29, 2022 An international team of researchers (Austria, Germany) shaped a laser pulse with a spatial light modulator which interacted with a counter-propagating, synchronized pulsed electron beam in a modified scanning electron microscope. This enabled imprinting on demand transverse phase shifts to the electron wave, enabling unprecedented control over electron beams. They demonstrated the potential of this innovative technology by creating convex and concave electron lenses and by generating complex electron intensity distributions. According to the researchers their experiments paved the way for wavefront shaping in pulsed electron microscopes with thousands of programmable pixels. In contrast to […]
Tag Archives: Imaging technology
‘Optical magic’: New flat glass enables optimal visual quality for augmented reality goggles
Phys.org September 28, 2022 Augmented reality (AR) glass needs to be highly transparent over almost the entire visible spectrum. In traditional AR there is a tradeoff in terms of quality and brightness between the external scene and the contextual information you want to visualize. A team of researchers in the US (Columbia University, City University of New York) has demonstrated nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light, realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected. This is made possible by quasi-bound state in the continuum encoded […]
Light derails electrons through graphene (w/video)
Nanowerk March 24, 2022 An international team of researchers (Spain, USA – Columbia University, Japan, Singapore) showed that by applying circular polarized infrared light onto the bilayer graphene device, they could selectively excite one specific valley population of electrons in the material, which generated a photovoltage perpendicular to the usual electron flow. By engineering the device and setup in such a way that current only flows with light illumination, they were able to avoid the background noise that hampers measurements and achieved a sensitivity in the detection several orders of magnitude better than any other 2D material. They could control […]
‘Fingerprint’ machine learning technique identifies different bacteria in seconds
Phys.org March 4, 2022 Researchers in South Korea have demonstrated a markedly simpler, faster, and effective route to classify signals of two common bacteria E. coli and S. epidermidis and their resident media without any separation procedures by using surface-enhanced Raman spectroscopy (SERS) analysis boosted with a newly proposed deep learning model named dual-branch wide-kernel network (DualWKNet). With outstanding classification accuracies up to 98%, the synergistic combination of SERS and deep learning serves as an effective platform for “separation-free“ detection of bacteria in arbitrary media with short data acquisition times and small amounts of training data. Universal and fast bacterial […]
Wallet-sized device focuses terahertz energy to generate high-resolution images
EurekAlert February 18, 2022 Researchers at MIT have built the most precise, electronically steerable, terahertz antenna array, called “reflectarray” which contains nearly 10,000 antennas onto a device the size of a credit card. It can precisely focus a beam of terahertz energy on a tiny area and control it rapidly with no moving parts. The researchers demonstrated the device by generating 3D depth images with military-grade resolution and twice the angular resolution of those produced by a large radars. The new phase shifter design consumes no power at all. The reflectarray uses one main source of energy to fire terahertz […]
Color-changing magnifying glass gives clear view of infrared light
Phys.org December 2, 2021 An international team of researchers (UK, Belgium, Spain) used a single layer of molecules to absorb the mid-infrared light inside their vibrating chemical bonds. These shaking molecules donate their energy to visible light that they encounter, ‘upconverting’ it to emissions closer to the blue end of the spectrum, which can then be detected by visible-light cameras. The challenge was to make sure the quaking molecules met the visible light quickly enough. They devised a way to sandwich single molecular layers between a mirror and tiny chunks of gold to twist and squeeze light. The researchers emphasize […]
Diffractive optical networks reconstruct holograms instantaneously without a digital computer
Phys.org November 2, 2021 Researchers at UCLA have developed a computer-free, all-optical process for the reconstruction of holograms using diffractive networks, diffractive network is an all-optical processor composed of a set of spatially engineered diffractive surfaces that collectively compute a desired transformation of an input light field through light-matter-interaction and diffraction. The spatial features of a diffractive network are trained and optimized for a given task using deep learning in a computer. After the training is complete, the diffractive surfaces can be fabricated and assembled to form a physical network that can all-optically reconstruct an input hologram of an unknown […]
Tuning transparency and opacity
Phys.org October 18, 2021 Recently, a new type of wavefront shaping was introduced where the extinction is manipulated instead of the scattered intensity. The underlying idea is that upon changing the phases or the amplitudes of incident beams, the total extinction will change due to interference described by the cross terms between different incident beams. Researchers in the Netherlands have experimentally demonstrated the mutual extinction and transparency effects in scattering media a human hair and a silicon bar. They sent two light beams with a variable mutual angle on the sample. Depending on the relative phase of the incident beams, they […]
Exploring quantum correlations of classical light source for image transmission
Phys.org August 31, 2021 Researchers in China formulated a density matrix to fully describe two-photon state within a thermal light source in the photon orbital angular momentum (OAM) Hilbert space. They proved the separability, i.e., zero entanglement of the thermal two-photon state. Still, they revealed the hidden quantum correlations in terms of geometric measures of discord. By mimicking the original protocol of quantum teleportation, they demonstrated that the non-zero quantum discord can be utilized to transmit a high-dimensional OAM state at the single-photon level. It was found that the information of all parameters that characterize the original state can still […]
Non-line-of-sight imaging with picosecond temporal resolution
Phys.org August 12, 2021 Non-line-of-sight (NLOS) imaging enables monitoring around corners and is promising for diverse applications. The resolution of transient NLOS imaging is limited to a centimeter scale, mainly by the temporal resolution of the detectors. Researchers in China have constructed an up-conversion single-photon detector with a high temporal resolution of ∼1.4 ps and a low noise count rate of 5 counts per second (cps). The detector operates at room temperature, near-infrared wavelength. They demonstrated high-resolution and low-noise NLOS imaging. The system can provide a 180 μm axial resolution and a 2 mm lateral resolution, which is more than […]