Researchers at Chalmers University of Technology in Sweden have reported that a single laser pulse can create complex, ordered nanostructure systems. This previously unobserved phenomenon has just beeen described in an article in the scientific journal Nature Photonics. "We have discovered a method for controlling the pattern into which the nanoparticles organize themselves," says physicist Dinko Chakarov, one of the authors of the article. The complex nanostructures that are created may find applications in fibre optics, optical sensors and advanced light emitting diodes and lasers.
The researchers started with a layer of disordered nanoparticles of gold or silver on a membrane of nanometre thickness. The patterning is a consequence of several transformations of the light, which finally results in partial melting and moving of the nanoparticles.
First, the light is caught by the particles, resulting in resonant swinging back and forth of the particle electrons (so called localized plasmon resonances). This specific excitation gives rise to scattering and coupling of electromagnetic energy into trapped, waveguided modes of the thin membrane. The edges of the membrane cause a standing wave pattern to be formed.
The end result is hot and cold zones of a specific periodicity on the membrane surface, and if the laser light energy is high enough, the field energy in the hot zones is high enough to melt and move the gold particles. All of this occurs within a few nanoseconds or even faster, and the resulting patterns have dimensions that can be both smaller and larger than the laser wavelength.
The results demonstrate that complex nanostructured systems can be fabricated and manipulated by a single laser pulse. In addition, the study shows in a very concrete manner that assemblies of optically active nanoparticles can be used to trap light in a waveguide (membrane or fibre) with nanometer dimensions.
The researchers have shown that the pattern can be controlled by varying several parameters: the laser light angle, wavelength and polarization, as well as the membrane thickness and the type of particles on the membrane. The discovery contributes to the understanding of the fundamental interaction between light and matter.
Researchers from the Department of Chemistry at the Royal Institute of Technology (KTH) in Stockholm, Sweden, have managed to construct a molecular catalyzer that can oxidize water to oxygen very rapidly. In fact, these KTH scientists are the first to reach speeds similar to those is nature ... more
Researchers at Chalmers University of Technology have built a very simple nanoantenna that directs red and blue colours in opposite directions, even though the antenna is smaller than the wavelength of light. The findings – published in the online journal Nature Communications – can lead to ... more
Researchers at Chalmers University of Technology in Sweden have developed a new measurement technology that makes use of optical resonances in nanoparticles. The method, which opens new possibilities in the field of catalytics, will be published in the journal Science for November and is al ... more
It is time to stop discussing whether electric cars are good or bad. Instead industry, authorities and policy-makers need to work together to make them as eco-friendly as possible. This is the view taken by Anders Nordelöf, a researcher at Chalmers University of Technology. In a recent thes ... more
Scarce metals are found in a wide range of everyday objects around us. They are complicated to extract, difficult to recycle and so rare that several of them have become “conflict minerals” which can promote conflicts and oppression. A survey at Chalmers University of Technology now shows t ... more
By combining graphene with another two-dimensional material, researchers at Chalmers University of Technology have created a prototype of a transistor-like device for future computers, based on what is known as spintronics. Spin as the information carrier can result in electronics that are ... more