Phys.org October 24, 2022 After experimentally studying the optical properties of dielectric reflective metalenses including their off-axis focusing performance, researchers in Saudi Arabia proposed reflective metalens based on titanium dioxide (TiO2) and silicon dioxide (SiO2), which operate at a visible wavelength of 0.633 µm. Unlike conventional reflective metalenses based on metallic mirrors, the proposed device was designed based on a modified parabolic phase profile and was integrated onto a dielectric distributed Bragg reflector periodic structure to achieve high reflectivity with five dielectric pairs. The focusing efficiency characteristics of the metalens were experimentally studied for beam angles of incidence between 0∘ […]
New approach to ‘cosmic magnet’ manufacturing could reduce reliance on rare earths in low-carbon technologies
Science Daily October 24, 2022 Tetrataenite, an iron-nickel alloy with a particular ordered atomic structure, is one of the most promising material to replace rare earth magnet. It forms over millions of years as a meteorite slowly cools, giving the iron and nickel atoms enough time to order themselves into a particular stacking sequence within the crystalline structure, ultimately resulting in a material with magnetic properties approaching those of rare-earth magnets. The 1960s technique for forming tetrataenite is not suitable for mass production. An international team of researchers (Italy, Austria, UK) found a possible alternative that doesn’t require millions of […]
The next wonder semiconductor
Science Daily October 25, 2022 Cubic boron arsenide (BAs) is promising for microelectronics thermal management because of its high thermal conductivity. Recently, its potential as an optoelectronic material was explored. However, it remains challenging to measure its photocarrier transport properties because of small sizes of available high-quality crystals. A team of researchers in the US (UC Santa Barbara, University of Houston) used scanning ultrafast electron microscopy (SUEM) to directly visualize the diffusion of photocarriers in BAs single crystals. They observed ambipolar diffusion at low optical fluence with persistent hot carrier dynamics for above 200 ps, which could likely be attributed […]
Penguin feathers may be secret to effective anti-icing technology
Phys.org October 24, 2022 The body feathers of perpetually ice-free penguins are very good natural examples of anti-icing surfaces, which use two different mitigation strategies for the two disparate problems – water adhesion and ice adhesion. Researchers in Canada constructed the form of the feather’s wire-like structure and decorated it with superimposed nanogrooves by laser micromachining fine woven wire cloths. Post-processing techniques also allowed them to isolate the role of surface chemistry by creating both hydrophilic and hydrophobic versions of the synthetic anti-icing surfaces. Their results showed that water-shedding and ice-shedding characteristics are indeed derived from different physical functions of […]
Researchers develop laser that could ‘reshape the landscape of integrated photonics’
Phys.org October 24, 2022 A team of researchers in the US (University of Rochester, UC Santa Barbara, Caltech, Clemson University) has developed multi-color integrated laser that emits high-coherence light at telecommunication wavelengths allows laser-frequency tuning at record speeds and can be configured at the visible band. Using a hybrid integrated III-V/Lithium Niobate structure they demonstrated several essential capabilities that have not existed in previous integrated lasers. These include a record-high frequency modulation speed of 2 exahertz/s and fast switching at 50 MHz, both of which are made possible by integration of the electro-optic effect. The device co-lases at infrared and […]
A Single Laser Transmitted a Second’s Worth of Internet Traffic in Record Time
Science Alert October 25, 2022 As essential core technologies for optical fibre communication are approaching their limits of size, speed and energy-efficiency, there is a need for new technologies that offer further scaling of data transmission capacity. An international team of researchers (Denmark, Sweden, Japan) has shown that a single optical frequency-comb source based on a silicon nitride ring resonator supports data capacities in the petabit-per-second regime. They experimentally demonstrated transmission of 1.84 Pbit s–1 over a 37-core, 7.9-km-long fibre using 223 wavelength channels derived from a single microcomb ring resonator producing a stabilized dark-pulse Kerr frequency comb. They presented a theoretical […]
Speeding up DNA computation with liquid droplets
Nanowerk October 22, 2022 Bottom-up engineering of synthetic condensates advances our understanding of the organizing principle of condensates. It also enables the synthesis of artificial systems with novel functions. However, building synthetic condensates with a predictable organization and function remains challenging. Researchers in South Korea used DNA as a building block to create synthetic condensates that are assembled through phase separation. The programmability of intermolecular interactions between DNA molecules enabled the control over various condensate properties including assembly, composition, and function. Similar to the way intracellular condensates are organized, DNA clients were selectively partitioned into cognate condensates. They demonstrated how […]
Tandem solar cells with perovskite: Nanostructures help in many ways
Science Daily October 24, 2022 Perovskite–silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Researchers in Germany have developed perovskite–silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. They showed a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enabled a greatly increased fabrication yield from 50% to 95%. The open-circuit voltage was improved by 15 mV due to the enhanced optoelectronic properties […]
Tapping hidden visual information: An all-in-one detector for thousands of colors
Science Daily October 20, 2022 Miniaturized computational spectrometers, which can obtain incident spectra using a combination of spectral responses and reconstruction algorithms, are essential for on-chip and implantable applications. Highly sensitive spectral measurement using a single detector allows the footprints of such spectrometers to be scaled down while achieving spectral resolution approaching that of benchtop systems. An international team of researchers (Finland, USA – Oregon State University, South Korea, UK, China) has developed a high-performance computational spectrometer based on a single van der Waals junction with an electrically tunable transport-mediated spectral response. They achieved high peak wavelength accuracy, high spectral […]
Tracking raindrops, one molecule at a time
Science Daily October 25, 2022 A team of researchers in the US (U Mass. Amherst, University of Alaska) studied the mechanisms of precipitation deuterium excess (d-excess) seasonality in low-latitudes and mid-latitudes through a new analysis of precipitation isotope databases along with climate reanalysis products and moisture tracking models. The ultimate d-excess signals are produced after complex modulations by several reinforcing or competing processes. They developed a simple seasonal water storage model to show that contributions of previously evaporated residual water storage and higher transpiration fractions may lead to relatively low d-excess in evapotranspiration fluxes during periods of enhanced continental moisture […]