Phys.org August 14, 2024 Toroidal electromagnetic pulses have been recently reported as non-transverse, space-time non-separable topological excitations of free space. However, their propagation dynamics and topological configurations have not been comprehensively experimentally characterized. The existing generators were limited in optical and terahertz domains; however, the feasibility and significance of generating such pulses at microwave frequencies have been overlooked. An international team of researchers (USA – Illinois Institute of Technology, China, Singapore) found that microwave toroidal pulses could be launched by a transient finite-aperture broadband horn antenna emitter, as an electromagnetic counterpart of “air vortex cannon.” Using this generator, they experimentally […]
Tag Archives: Optical communications
Researchers develop technology to mass produce quantum dot lasers for optical communications
Phys.org June 28, 2024 To produce 75 °C continuous-wave operation research in South Korea investigated InAs/GaAs quantum dot laser diodes (QDLDs) on a GaAs substrate grown by utilizing all-metalorganic chemical vapor deposition technology with a p-AlGaAs cladding layer. The InAs quantum dots (QDs) in a dot-in-a-well (DWELL) structure formed by engineering the strained bottom InGaAs layer were successfully grown without detectable clusters, making it possible to increase the number of DWELL stacks effectively. The results of electron-channeling contrast imaging revealed that dislocations in the p-cladding layer were generated due to the accumulative strain of the DWELL and low-temperature growth. The […]
Looking at optical Fano resonances under a new light
Phys.org March 19, 2021 Fano resonances are conventionally understood as sharp spectral features that can be excited only by plane waves with specific frequencies and incident angles. Researchers at the City University of New York proved that they can be tailored to resonate only when excited by a frequency, polarization, and wavefront of choice. This generalization reveals that Fano systems are characterized by eigenwaves that scatter to their time-reversed image upon reflection. They showed that the selected wavefront is locally retroreflected everywhere across the device. These results show that conventional Fano resonances are a subset of a broader dichroic phenomenon […]
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 […]
Painting with light: Novel nanopillars precisely control intensity of transmitted light
EurekAlert September 4, 2020 By shining white light on a glass slide stippled with millions of tiny titanium dioxide pillars, an international team of researchers (China, USA – NIST, University of Maryland) has reproduced luminous hues and subtle shadings of a painting. By adding or dropping a particular color, or wavelength, of light traveling in an optical fiber, scientists can control the amount of information carried by the fiber. By altering the intensity, researchers can maintain the brightness of the light signal as it travels long distances in the fiber. The approach has potential applications in improving optical communications and […]