Tiny particles with varied shapes scatter light in useful and unusual ways.
A study into the way nanoparticles scatter light could lead to simpler and smaller optical nanoantennas with improved directivity and efficiency — crucial components for the next generation of advanced photonic devices.
The strength and direction of light scattering can be controlled by carefully selecting a nanostructure’s shape and refractive index. © A*STAR Data Storage Institute
Boris Luk’yanchuk and co-workers from the Agency for Science, Technology and Research (A*STAR) Data Storage Institute, Singapore, together with a collaborator in St. Petersburg University, Russia, undertook a detailed numerical investigation of the light scattering characteristics of dielectric nanoparticles of different shapes with high refractive indexes (larger than 2). They focused particularly on nanoscale spheres and spheroids.
By carefully selecting the nanoparticle’s shape and refractive index, the team discovered they could use the interference between the particle’s electric and magnetic dipole resonances to control and optimize the strength and direction of its light scattering.
For example, they found that for a spheroid particle with a refractive index of 3.5, scattering in the forward direction can be maximized if the spheroid’s major axis is just over twice the length of its minor axis.
Steering the flow of light by manipulating the nanoparticle’s aspect ratio is potentially useful in many applications, for example to maximize the light captured by a solar cell or to make artificially-engineered metasurfaces that can cause light to flow in interesting and unusual ways.
“Dielectric particles with optimized shapes which behave as very efficient directional antennas can be used in sensing devices, transmission lines, metasurfaces with numerous uses and in many other devices such as negative refractive index lenses, optical cloaking devices or nanolasers,” explained Luk’yanchuk, the lead researcher in the study.
“The fascinating properties of dielectric materials with high refractive indexes are related to their ability to have both electric and magnetic dipoles. It makes it possible to produce different interference phenomena in their scattering, like Fano resonances for example. We are trying to use these effects to produce different types of nanoscale devices and metasurfaces.”
According to Luk’yanchuk, the physics of this scattering is valid and scalable across the electromagnetic spectrum and thus their approach could be applied not only at optical and infrared frequencies, but at microwave frequencies as well, provided that suitable transparent particles with a sufficiently high refractive index are used.
“At optical frequencies, for example, there are many suitable materials like titanium dioxide, silicon, germanium, gallium arsenide and other group IV and III-V semiconductors,” commented Luk’yanchuk. “The possible limitation would be frequencies higher than the visible range, like the ultraviolet, where no high-index transparent dielectrics are readily available.”
The A*STAR-affiliated researchers contributing to this research are from the Data Storage Institute
 Luk’yanchuk, B. S., Voshchinnikov, N. V., Paniagua-Dominguez, R. & Kuznetsov, A. I. Optimum forward light scattering by spherical and spheroid dielectric nanoparticles with high refractive index, ACS Photonics 2, 993–999 (2015).
Original article from A*STAR Research
A*STAR Research | Research SEA
Comet or asteroid? Hubble discovers that a unique object is a binary
21.09.2017 | NASA/Goddard Space Flight Center
First users at European XFEL
21.09.2017 | European XFEL GmbH
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
21.09.2017 | Physics and Astronomy
21.09.2017 | Life Sciences
21.09.2017 | Health and Medicine