Building images photon-by-photon to increase the information content provided by microscopes

Phys.org  February 6, 2024 A flawless recording of single-photon spatiotemporal information poses significant challenges for the microscope data acquisition (DAQ) system. An international team of researchers (Italy, Switzerland) has presented a DAQ module based on the digital frequency domain principle, able to record essential spatial and temporal features of photons. They used the module to extend the capabilities of established imaging techniques based on single-photon avalanche diode (SPAD) array detectors. They used the module to introduce a robust multispecies approach encoding the fluorophore excitation spectra in the time domain. By combining time-resolved stimulated emission depletion microscopy with image scanning microscopy, […]

A new wavelength of scientific exploration with single-photon detectors

Phys.org  January 31, 2024 Superconducting nanowire single-photon detectors (SNSPDs) are a mature photon-counting technology as demonstrated by their figures of merit such as high detection efficiencies and very low dark count rates. However, scaling SNSPDs to large array sizes for mid-infrared applications requires sophisticated readout architectures in addition to superconducting materials development. Researchers at NIST, Boulder, Colorado, developed an SNSPD array design that combined a thermally coupled row-column multiplexing architecture with a thermally coupled time-of-flight transmission line for mid-infrared applications. It required only six cables and could be scaled to larger array sizes. The demonstration of a 64-pixel array showed […]

Clear holographic imaging in turbulent environments

Phys.org   October 30, 2023 The existing deep-learning methods for holographic imaging often depend solely on the specific condition based on the given data distributions. One critical problem is how to guarantee the alignment between any given downstream tasks and pretrained models. Researchers in China analyzed the physical mechanism of image degradation caused by turbulence and proposed a swin transformer-based method, termed train-with-coherence-swin (TWC-Swin) transformer, which used spatial coherence (SC) as an adaptable physical prior information to precisely align image restoration tasks in the arbitrary turbulent scene. They designed light-processing system (LPR) which enabled manipulation of SC and simulation of any […]

Superlensing without a super lens: Physicists boost microscopes beyond limits

Phys.org  October 18, 2023 Imaging with resolutions much below the wavelength λ remains challenging at lower frequencies, where exponentially decaying evanescent waves are generally measured using a tip or antenna close to an object. Such approaches are often problematic because probes can perturb the near-field itself. Researchers in Australia have demonstrated that information encoded in evanescent waves can be probed further than previously thought, by reconstructing truthful images of the near-field through selective amplification of evanescent waves like a virtual superlens that images the near field without perturbing it. They quantified trade-offs between noise and measurement distance, experimentally demonstrated reconstruction […]

Unveiling the invisible: A bioinspired CMOS-integrated polarization imaging sensor

Phys.org  September 18, 2023 Chip-integrated, fast, cost-effective, and accurate full-Stokes polarimetric imaging sensors are highly desirable in many applications, but they remain elusive due to fundamental material limitations. Researchers at the State University of Arizona have developed a chip-integrated Metasurface-based Full-Stokes Polarimetric Imaging sensor (MetaPolarIm) by integrating an ultrathin (~600 nm) metasurface polarization filter array (MPFA) onto a visible imaging sensor with CMOS compatible fabrication processes. The MPFA has broadband dielectric-metal hybrid chiral metasurfaces and double-layer nanograting polarizers. This chip-integrated polarimetric imaging sensor enabled single-shot full-Stokes imaging (speed limited by the CMOS imager) with the most compact form factor, recorded high […]

Wifi can read through walls

Science Daily   September 11, 2023 Imaging still scenery with Wi-Fi is considerably challenging due to the lack of motion. The interaction of object edges with the incoming wave, dictated by the Geometrical Theory of Diffraction and the resulting Keller cones, presents new possibilities for imaging with WiFi via edge tracing. Researchers at UC Santa Barbara used the Geometrical Theory of Diffraction and the corresponding Keller cones to trace edges of the objects. They considered the impact of parameters such as curvature of a soft edge, edge orientation, distance to the receiver grid, transmitter location, and other parameters on edge-based WiFi […]

Scientists continue to push the boundaries of imaging techniques and reveal the mysterious world of molecules

Nanowerk  August 29, 2023 Researchers in Czech Republic have experimentally confirmed the correctness of a decades-old theory that assumed a non-uniform distribution of electron density in aromatic molecules, a phenomenon that significantly affects the physicochemical properties of molecules and their interactions. They presented the resolution of the π-hole on a single molecule which supports the theoretical prediction of its existence. Experimental measurements supported by theoretical calculations showed the importance of π-holes in the process of adsorption of molecules on solid-state surfaces. According to the researchers better knowledge of the distribution of the electron charge will help the scientific community to […]

Researchers devise new quantum photonics technique to create better holograms

Phys.org  July 10, 2023 It is possible to observe interference between independent light sources by measuring correlations in their intensities rather than their amplitudes. An international team of researchers (Canada, UK) applied this concept of intensity interferometry to holography. They combined a signal beam with a reference and measured their intensity cross-correlations using a time-tagging single-photon camera. The correlations revealed an interference pattern from which they reconstructed the signal wavefront in both intensity and phase. They demonstrated the principle with classical and quantum light, including a single photon. Since the signal and reference do not need to be phase-stable nor […]

All-optical, near-infrared imaging via ultra-thin structured films

Phys.org  May 26, 2023 Compared to metasurfaces composed of the periodic arrangement of nanoparticles, inverse membrane metasurfaces offer unique possibilities for supporting multipolar resonances, while maintaining small unit cell size, large mode volume and high field enhancement for enhancing nonlinear frequency conversion. An international team of researchers (UK, Australia, China, Hong Kong) theoretically and experimentally investigated the formation of bound states in the continuum (BICs) from silicon dimer-hole membrane metasurfaces, and demonstrated that BIC-formed resonance featured a strong and tailorable electric near-field confinement inside the silicon membrane films. They showed that by tuning the gap between the holes, it is […]

Capturing non-transparent ultrafast scenes

Phys.org  May 26, 2023 Real-time imaging modalities with ultrahigh temporal resolutions are required for capturing ultrashort events on picosecond timescales for unveiling many fundamental mechanisms in physics, chemistry, and biology. Current single-shot ultrafast imaging schemes operate only at conventional optical wavelengths, being suitable solely within an optically transparent framework. Researchers in Canada leveraged the unique penetration capability of terahertz radiation to demonstrate a single-shot ultrafast terahertz photography system that could capture multiple frames of a complex ultrafast scene in non-transparent media with sub-picosecond temporal resolution. By multiplexing an optical probe beam in both the time and spatial-frequency domains, they encoded […]