Researchers demonstrate angular accelerating light
Light must travel in a straight line and at a constant speed, or so the laws of nature suggest. Now, researchers at the University of the Witwatersrand in Johannesburg have demonstrated that laser light traveling along a helical path through space, can accelerate and decelerate as it spins into the distance.
This is the first time that angular acceleration has been observed with light, and is therefore likely to lead to new applications using these structured light fields.
The results are contained in a research paper by Professor Andrew Forbes from the Wits School of Physics and his collaborators¹, published online this week in the journal, Physical Review A. Titled: Accelerated rotation with orbital angular momentum modes, the work has also been selected as a highlighted paper by the editors.
Forbes, who joined the Wits School of Physics in March this year, is heading up the new Structured Light Laboratory that focuses on creating custom light fields using digital holograms. The research group creates complex light that exhibits interesting physical properties, which they exploit for a range of applications.
Previously, Forbes and his collaborators have shown that light could be made to spin. In this recent work they demonstrated the first realisation of angular accelerating light and showed that light could also be made to accelerate and decelerate. This acceleration can be controlled with a single parameter that is readily tuned with a digital hologram written to a standard LCD screen, much like your LCD television at home, but just a much smaller version.
"Our angular accelerating fields rely on combinations of orbital angular momentum - so-called twisted light," says Forbes. Light carrying orbital angular momentum is created by twisting the wave-front of light into a helical shape, forming a spiral. Usually this twist in the light's wave-front is smooth, like a spiral staircase with regular steps. "Our novelty was to realise that by twisting the helicity of these beams in a non-linear fashion, the result would be a propagation dependent angular velocity," he explains. In other words, the light spins at a non-constant speed, resulting in angular acceleration.
In fact, the light speeds up and slows down as it travels, periodically switching from one mode to the other. Following its helical path through space, the helix appears to wind up very tightly as it accelerates, and winds down very loosely as it decelerates. It is intriguing that by "twisting the twist", nature provides an additional momentum to the field causing it to accelerate as it spins.
The team expects this new optical field to be of interest as a tool to study some fundamental physical processes with light, as well as a tool in optically driving micro-fluidic flow.
¹The idea was conceived by Forbes who led the collaboration with Christian Schulze and Michael Duparré (University of Jena, Germany), Ronald Rop (Eggerton University, Kenya), and Filippus Roux and Angela Dudley (Council for Scientific and Industrial Research, South Africa).
Erna van Wyk | EurekAlert!
First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester
Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy