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Polarimetric imaging has a wide range of applications for uncovering features invisible to human eyes and conventional imaging sensors. Chip-integrated, fast, cost-effective, and accurate full-Stokes polarimetric imaging sensors are highly desirable in many applications, which, however, remain elusive due to fundamental material limitations. Here we present a chip-integrated Meta surface-based Full-Stokes Polar imetric Im aging sensor (MetaPolarIm) realized by integrating an ultrathin (~600 nm) metasurface polarization filter array (MPFA) onto a visible imaging sensor with CMOS compatible fabrication processes. The MPFA is featured with broadband dielectric-metal hybrid chiral metasurfaces and double-layer nanograting polarizers. This chip-integrated polarimetric imaging sensor enables single-shot full-Stokes imaging (speed limited by the CMOS imager) with the most compact form factor, records high measurement accuracy, dual-color operation (green and red) and a field of view up to 40 degrees. MetaPolarIm holds great promise to enable transformative applications in autonomous vision, industry inspection, space exploration, medical imaging and diagnosis. We present a chip-integrated Meta surface-based Full-Stokes Polar imetric Im aging sensor (MetaPolarIm) with ultra-compactness, record high measurement accuracy, dual color operation, and a field of view up to 40 degrees.

The manipulation and characterization of light polarization states are essential for many applications in quantum communication and computing, spectroscopy, bioinspired navigation, and imaging. Chiral metamaterials and metasurfaces facilitate ultracompact devices for circularly polarized light generation, manipulation, and detection. Herein, we report bioinspired chiral metasurfaces with both strong chiral optical effects and low insertion loss. We experimentally demonstrated submicron-thick circularly polarized light filters with peak extinction ratios up to 35 and maximum transmission efficiencies close to 80% at near-infrared wavelengths (the best operational wavelengths can be engineered in the range of 1.3–1.6 µm). We also monolithically integrated the microscale circular polarization filters with linear polarization filters to perform full-Stokes polarimetric measurements of light with arbitrary polarization states. With the advantages of easy on-chip integration, ultracompact footprints, scalability, and broad wavelength coverage, our designs hold great promise for facilitating chip-integrated polarimeters and polarimetric imaging systems for quantum-based optical computing and information processing, circular dichroism spectroscopy, biomedical diagnosis, and remote sensing applications.

Graphene is an attractive material for all-optical modulation because of its ultrafast optical response and broad spectral coverage. However, all-optical graphene modulators reported so far require high pump fluence due to the ultrashort photo-carrier lifetime and limited absorption in graphene. We present modulator designs based on graphene-metal hybrid plasmonic metasurfaces with highly enhanced light-graphene interaction in the nanoscale hot spots at pump and probe (signal) wavelengths. Based on this design concept, we have demonstrated high-speed all-optical modulators at near and mid-infrared wavelengths (1.56 μm and above 6 μm) with significantly reduced pump fluence (1–2 orders of magnitude) and enhanced optical modulation. Ultrafast near-infrared pump-probe measurement results suggest that the modulators’ response times are ultimately determined by graphene’s ultrafast photocarrier relaxation times on the picosecond scale. The proposed designs hold the promise to address the challenges in the realization of ultrafast all-optical modulators for mid-and far-infrared wavelengths.Ultrafast low-pump fluence all-optical modulation for near and mid-infrared wavelengths is demonstrated by enhancing the interaction between graphene and pump/probe light in the nanoscale “hot spots” of graphene-plasmonic hybrid metasurfaces.

Avian electrocutions are a global conservation problem. Power outages associated with electrocutions are problematic for electric utilities focused on delivering reliable electric power. We used contextual data, photographs, line voltage, outage type and assessments of power line components to quantify outage-causing avian electrocutions throughout each of Iran’s 31 provinces. We evaluated records of 222 avian-caused outages involving 235 electrocuted birds in 2018. Of these, 14.5% involved species of conservation concern, and a few (at least eight) sparked fires when the plumage of electrocuted birds ignited and fell into dry vegetation. Most avian-caused outages (96%) involved distribution voltages, and 91% involved phase-to-ground contacts attributable to grounded concrete pylons with grounded steel crossarms. These are the most common type of power line structure in Iran. Insulators were involved in 37% of outage-causing avian electrocutions, fused cutouts 29%, transformers 33%, and midspan collisions 1%. Given the numbers of these components in the electrical system, fused cutouts and transformers were involved in more outage-causing avian electrocutions than expected due to chance. The average body size of electrocuted birds was largest for incidents involving suspension insulators, smaller for birds electrocuted on other insulators, and smallest for electrocutions on fused cutouts and transformers. Given that most avian electrocutions do not cause outages and given the similarity across electric systems in the region, our findings likely indicate a much larger avian electrocution concern throughout the middle east. Retrofitting power line components to reduce avian contacts would reduce impacts to wildlife and improve the electrical system’s reliability, reduce costs associated with unplanned outages, and reduce risks associated power line ignitions of fires.

Electrical faults caused by power escaping electric systems can lead to power outages, equipment damage, and fires. Faults sometimes occur when birds perched on power structures are electrocuted. Distribution power lines supported by concrete and steel pylons are particularly fault-prone because small separations between conductors and grounded components allow even small birds to inadvertently create faults while being electrocuted. Most conservation solutions focus on covering energized wires and components to prevent contact by birds and, although usually effective when installed correctly, covers can sometimes be dislodged thus becoming ineffective. Glass Flake Epoxy (GFE) is a non-conductive thermoset plastic that can adhere to steel crossarms and not be dislodged. We hypothesized that GFE-coated crossarms might reduce faults (proxies for avian electrocutions), and we conducted laboratory and field trials to evaluate that hypothesis. In the laboratory, we found a 2000 micrometer (μm)-thick layer of GFE coating that created a dielectric strength of 12.30 ± 0.21 kV, which was sufficient to prevent the formation of a phase-to-ground fault on up to 20 kV distribution lines. This should allow birds to perch on metal crossarms without being electrocuted. In field trials, we substituted 24% of a 20 kV distribution pylon’s crossarms with GFE-treated crossarms and found that doing so correlated with a 28% decrease in faults. Although we did not measure avian electrocutions directly, our findings suggest GFE coatings may offer a novel method of reducing avian electrocutions on power lines.

The South Caucasus is an important region for the study of separatism. While separatist tendencies are present in a large number of South Caucasian ethnic groups, there are significant differences in the degree to which such tendencies have been realized. Why certain groups in the South Caucasus have been more successful than others in pursuing their separatist demands has yet to be adequately explained. The present study employs ethnic bargaining theory to examine the causes of this phenomenon and assesses separatism on the basis of the relationship between ethnic groups, the center, and patron states as well as the effect of ethnic bargaining tools on these relations. The authors hypothesize that ethnic bargaining tools, namely territorial concentration and external support, radicalize ethnic group demands and are directly related to the success of separatist movements. This descriptive-analytical investigation of ethnic separatism in the post-Soviet South Caucasus confirms this hypothesis.

Abstract Polarimetric imaging has a wide range of applications for uncovering features invisible to human eyes and conventional imaging sensors. Chip-integrated, fast, cost-effective, and accurate full-Stokes polarimetric imaging sensors are highly desirable in many applications, which, however, remain elusive due to fundamental material limitations. Here we present a chip-integratedMetasurface-based Full-StokesPolarimetricImaging sensor (MetaPolarIm) realized by integrating an ultrathin (~600 nm) metasurface polarization filter array (MPFA) onto a visible imaging sensor with CMOS compatible fabrication processes. The MPFA is featured with broadband dielectric-metal hybrid chiral metasurfaces and double-layer nanograting polarizers. This chip-integrated polarimetric imaging sensor enables single-shot full-Stokes imaging (speed limited by the CMOS imager) with the most compact form factor, records high measurement accuracy, dual-color operation (green and red) and a field of view up to 40 degrees. MetaPolarIm holds great promise to enable transformative applications in autonomous vision, industry inspection, space exploration, medical imaging and diagnosis.

Controllable strong interactions between a nanocavity and a single emitter is important to manipulating optical emission in a nanophotonic system but challenging to achieve. Herein a three-dimensional DNA origami, named as DNA rack (DR) is proposed and demonstrated to deterministically and precisely assemble single emitters within ultra-small plasmonic nanocavities formed by closely coupled gold nanorods (AuNRs). Uniquely, the DR is in a saddle shape, with two tubular grooves that geometrically allow a snug fit and linearly align two AuNRs with a bending angle < 10°. It also includes a spacer at the saddle point to maintain the gap between AuNRs as small as 2–3 nm, forming a nanocavity estimated to be 20 nm 3 and an experimentally measured Q factor of 7.3. A DNA docking strand is designed at the spacer to position a single fluorescent emitter at nanometer accuracy within the cavity. Using Cy5 as a model emitter, a ∼ 30-fold fluorescence enhancement and a significantly reduced emission lifetime (from 1.6 ns to 670 ps) were experimentally verified, confirming significant emitter-cavity interactions. This DR-templated assembly method is capable of fitting AuNRs of variable length-to-width aspect ratios to form anisotropic nanocavities and deterministically incorporate different single emitters, thus enabling flexible design of both cavity resonance and emission wavelengths to tailor light-matter interactions at nanometer scale.

Familial adenomatous polyposis (FAP) is an autosomal dominant disease with hundreds of colorectal adenomas in teenagers and progression to colorectal cancer if colectomy is not performed. We investigated the association of two phenotypic manifestations-oral mucosal vascular density (OMVD) and oral mucosal reflectance (OMR)––with FAP and patients with multiple colorectal adenomas. Thirty-three patients with FAP from 29 unrelated pedigrees with APC gene mutation, 5 with multiple adenomas and no known gene mutations, and 50 population controls were evaluated for the two different manifestations utilizing a photographic/spectrophotometric system capturing images and reflectance at various wavelengths. Statistical analysis was performed with student t test and test performance characteristics were calculated. There were no significant differences in demographic variables between the FAP and control group. A significant difference in OMVD between FAP patients and controls was noted, P  < 0.001. The sensitivity and specificity of oral mucosal vascular density for FAP was 91 and 90%, respectively. No association between this phenotypic manifestation and age or gender was found. All 5 patient with multiple polyps were positive for OMVD and the value was significantly higher than controls, P  = 0.002. No significant difference was noted in OMR between the two patient groups and controls. OMVD is a new phenotypic manifestation in patients with FAP and also may identify those with multiple adenomas without known gene mutation.