Nanowerk February 16, 2021 Electro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration, and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. An international team of researchers (Spain, Italy, Belgium) overcame this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. They integrated hafnium oxide and two-dimensional hexagonal boron nitride within the insulating section of a double-layer graphene EA modulator. This combination of materials […]
Author Archives: Hema Viswanath
Quantum Theory May Twist Cause And Effect Into Loops, With Effect Causing The Cause
Science Alert February 14, 2021 Quantum correlations violating Bell inequalities defy satisfactory causal explanations within the framework of classical causal models. The first challenge has been addressed through the recent development of intrinsically quantum causal models, allowing causal explanations of quantum processes – provided they admit a definite causal order, i.e., have an acyclic causal structure. An international team of researchers addresses causally nonseparable processes and offers a causal perspective on them through extending quantum causal models to cyclic causal structures. Among other applications of the approach, it is shown that all unitarily extendible bipartite processes are causally separable and […]
Researchers explore using light to levitate discs in the mesosphere
Phys.org February 15, 2021 To improve weather prediction sensors need to be sent to mesosphere. The satellites and rockets currently used have problems as the air is too thick and friction and heat would make long-duration flights impractical. Researchers at the University of Pennsylvania constructed and demonstrated light-driven levitation of macroscopic polymer films with nanostructured surface as candidates for long-duration near-space flight. The disks were made of 0.5-micron-thick mylar film coated with carbon nanotubes on one side. When illuminated with light intensity comparable to natural sunlight, the polymer disk heats up and interacts with incident gas molecules differently on the […]
Scientists manipulate magnets at the atomic scale
Science Daily February 12, 2021 An international team of researchers (the Netherlands, Ukraine, Russia, Belgium, UK) shows that light-driven phonons can be utilized to coherently manipulate macroscopic magnetic states. Intense mid-infrared electric field pulses tuned to resonance with a phonon mode of the archetypical antiferromagnet DyFeO3 induce ultrafast and long-living changes of the fundamental exchange interaction between rare-earth orbitals and transition metal spins. Non-thermal lattice control of the magnetic exchange, which defines the stability of the macroscopic magnetic state, allows picosecond coherent switching between competing antiferromagnetic and weakly ferromagnetic spin orders. The discovery emphasizes the potential of resonant phonon excitation […]
Quickly identify high-performance multi-element catalysts
Eurekalert February 17, 2021 Many electrochemical reactions go through several steps. Each should be optimized on a catalyst surface if possible, but different requirements apply to each step. With the example of the oxygen reduction reaction, an international team of researchers (Denmark, Germany) showed that for high entropy alloys comprising five or more principal elements, by utilizing a data‐driven discovery cycle, the multidimensionality challenge raised by this catalyst class can be mastered. Iteratively refined computational models predict activity trends around which continuous composition‐spread thin‐film libraries are synthesised. High throughput characterisation datasets are then used as input for refinement of the […]
This robot doesn’t need any electronics
Science Daily February 17, 2021 Pneumatically actuated soft robots are controlled with bulky and expensive electromechanical components. Researchers at UC San Diego have created a soft-legged robot using simple pneumatic circuits without any electronic components. Locomotive gaits are produced using ring oscillators composed of soft valves that generate oscillating signals analogous to biological central pattern generator neural circuits, which are acted upon by pneumatic logic components in response to sensor inputs. The robot requires only a constant source of pressurized air to power both control and actuation systems. The circuits generate walking gaits with three degrees of freedom per leg […]
A sharper look at the interior of semiconductors
Science Daily February 17, 2021 To investigate complex, functional, nanoscopic structures of semiconductor devices researchers in Germany have developed an imaging procedure using extreme ultraviolet coherence tomography. It is based on optical coherence tomography used in ophthalmology. They demonstrated the method at a laser-driven broadband extreme ultraviolet radiation source, based on high-harmonic generation. They showed that, besides nanoscopic axial resolution, the spectral reflectivity of all layers in a sample can be obtained using algorithmic phase reconstruction. This provides localized, spectroscopic, material-specific information of the sample. The method can be applied in semiconductor production, lithographic mask inspection, or quality control of multilayer […]
Wafer-scale production of graphene-based photonic devices
Science Daily February 11, 2021 Graphene has been recently proposed to be integrated with silicon photonics to meet the challenges of next generation optical communication to increase the available bandwidth while reducing the size, cost, and power consumption of photonic integrated circuits. An international team of researchers (Italy, UK) focused on graphene photodetectors for high speed datacom and telecom applications based on the photo-thermo-electric effect, allowing for direct optical power to voltage conversion, zero dark current, and ultra-fast operation. They reported on a chemical vapour deposition graphene photodetector based on the photo-thermoelectric effect, integrated on a silicon waveguide, providing frequency […]
Top 10 Science and Technology Inventions for the Week of February 12, 2021
01. Scientists create armor for fragile quantum technology 02. Silicon waveguides move us closer to faster, light-based logic circuits 03. UMass Amherst team helps demonstrate spontaneous quantum error correction 04. ‘Multiplying’ light could be key to ultra-powerful optical computers 05. Capturing Free-Space Optical Light for High-Speed WiFi 06. Inductance based on a quantum effect has the potential to miniaturize inductors 07. ‘Magnetic graphene’ forms a new kind of magnetism 08. New concept for rocket thruster exploits the mechanism behind solar flares 09. Quantum effects help minimize communication flaws 10. Quantum systems learn joint computing And others… 21 per cent of […]
21 per cent of all citations go to the elite
Science Daily February 9, 2021 Researchers in Denmark used a linked dataset of more than 4 million authors and 26 million scientific papers spanning 15 years and 118 scientific disciplines to quantify trends in cumulative citation inequality and concentration at the author level. They found that a small stratum of elite scientists accrues increasing citation shares, and that citation inequality is on the rise across the natural sciences, medical sciences, and agricultural sciences. The rise in citation concentration has coincided with a general inclination toward more collaboration. While increasing collaboration and full-count publication rates go hand in hand for the […]