Optical tweezers and spanners are about to become more sophisticated. A group of physicists in Germany has just demonstrated, for the first time, the existence of a novel, transverse effect pertaining to light beams used for optical trapping, called photonic wheel.
Photonic wheels : for drag racing at nano scale
This means that scientists will now have full rotational control over the micro- or nanoscale objects trapped in the tweezers’ optical beam. Peter Banzer and colleagues from the Max Planck Institute for the Science of Light, in Erlangen, Germany, just published their findings in the Journal of the European Optical Society Rapid Publications. The authors speculate that, under favourable low viscosity condition, this approach could lead to spinning a trapped particle that will then start moving like a spinning top, as soon as the trapping laser beam is switched off, thus creating the conditions for a nano drag race (see figure).
Due to their lack of mass, photons do not behave intuitively. Rather, they have characteristics of their own. They can be circularly polarised, for example. This means their electric field spins around the propagation axis—a characteristic described as angular momentum, which is parallel to the direction in which the photon travels. This longitudinal angular momentum is akin to that of aircraft propellers, aligned with the direction in which the aircraft travels.
Banzer and colleagues first predicted the new capability theoretically. They then confirmed it through experimental work, using a highly focused light beam with a special polarisation. They used a single metallic nanoparticle to probe the beam in the focal plane. Since there is a measurable deformation of the beam shape in that plane, it proves the existence of a purely transverse angular momentum in the beam for the investigated scheme.
Combining this newly discovered photonic wheel with conventional beams gives full rotational control when manipulating particles. This opens the possibility of new applications such as nanomixers and micromachines in addition to application in quantum optics and nano-optics.
Dr. Sabine König | Max-Planck-Institut
Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes
Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
18.01.2018 | Life Sciences
18.01.2018 | Life Sciences
18.01.2018 | Earth Sciences