Subscribe free to our newsletters via your
. 24/7 Space News .




ENERGY TECH
Light in the Moebius strip
by Staff Writers
Munich, Germany (SPX) Feb 18, 2015


Single-sided strip: A Mobius strip is twisted so that it has only one surface and one edge. Image courtesy Peter Banzer and MPI for the Science of Light.

Physics sometimes borders on light art. An international team headed by researchers from the Max Planck Institute for the Science of Light and Friedrich-Alexander-Universitaet Erlangen-Nuremberg (FAU), can easily compete with the light artists, at least as far as the skill of forming light is concerned.

In their most recent work they have wound a light wave into a Moebius strip: a strip that is formed into a closed loop, one of its ends being twisted through 180 with respect to the other one so that the strip has only one edge and one surface.

The physicists use these tricks not only to prove how precisely they can meanwhile manipulate light, they are also creating tools which could be interesting for nanotechnology.

A Moebius strip can irritate our perception. At first sight, the strip has two sides and two edges just like a normal ring made from a strip of paper, for example. If you follow one side or one edge with your finger, however, you arrive at the other side or edge after one circuit.

The geometric form is named after the mathematician August Ferdinand Moebius who, simultaneously with his fellow mathematician Johann Benedict Listing, was the first to describe it with equations. This kind of structure is found only rarely in nature, although there is a protein, for example, which is shaped like a Moebius strip.

It is more often to be found in engineering, in some gearboxes, for example, or as part of the construction principle of a fusion reactor that is intended to generate energy from the fusion of hydrogen to helium as occurs in the Sun.

Just as a Moebius strip is used in technical applications in the macroworld, it could also be useful in nanotechnology, for processing materials, for example. The Moebius strip generated from laser light by the scientists from the Max Planck Institute for the Science of Light and Friedrich-Alexander-Universitaet Erlangen-Nuremberg (FAU), among others, could be the appropriate optical tool to produce the corresponding nanoscopic structures from a material.

"Our optical Moebius strip also opens up new possibilities, however, such as using optical tweezers to guide microparticles and nanoparticles on complex paths," says Peter Banzer, Leader of a Research Group at the Max Planck Institute in Erlangen, who developed the concept for the single-sided strip of light together with Ebrahim Karimi from the University of Ottawa. Biologists use optical tweezers to manoeuvre cells under a microscope, for instance, and material scientists use them as well to manipulate microparticles and nanoparticles in tiny machines.

A Moebius strip at the focal point of two highly focused laser beams
But before the Erlangen-based researchers found the Moebius strip with their optical instruments, they calculated under which conditions such a structure is generated. They based their work on an idea by Isaac Freund at Bar-Ilan University in Israel, who was the first to suggest that a Moebius strip can be generated using two crossed laser beams.

"We've modified this approach in such a way that we obtain the structure in the focus of two beams where both are also very highly focussed," explains Peter Banzer.

For the experiment to work, the researchers have first to carefully prepare the two laser beams in the same beam path. The procedure starts with a single laser beam. The researchers begin by sending it through a filter which polarises light waves in such a way that their electric field vector rotates clockwise about its direction of propagation. This type of light is called right-hand circularly polarised by physicists.

A q-plate rotates and delays one part of the laser beam
The researchers in Erlangen then direct the beam, which is rotating in the clockwise direction through a q-plate, an optical element developed by Lorenzo Marrucci and Ebrahim Karimi at the University of Naples.

This element essentially comprises many layers of liquid crystal molecules between two glass panes, it being possible to apply an electric voltage to one of these cells. At a particular voltage, the q-plate rotates the polarisation of one part of the beam in the direction which is opposite to the polarisation of the other part of the beam. The waves of one-half of the beam thus then rotate anti-clockwise with respect to their direction of propagation.

At the same time, the q-plate delays this part of the laser light to differing degrees at different locations. Physicists call this a position-dependent phase shift of one part of the beam. The phase characterises an oscillation and states at which point of its wave motion it is at a particular time. This causes the electromagnetic field of the light waves to point into very different directions at different positions in the beam cross-section in one part of the beam.

When the two parts of the beam with the different characteristics are superimposed, they behave like a single laser beam. Peter Banzer and his colleagues exploit this when they send the laser light through the objective lens of a microscope that acts as a powerful lens. The lens focuses the light to a focal point.

The outer light waves are diffracted to a much greater extent than the inner ones so that the electromagnetic fields of the light waves in the focal point oscillate in very different directions, depending on their position in the beam cross-section. And as the theoretical considerations showed, this results in a constellation of the polarisation traced along a circle around the focal point which closes to form a Moebius strip. This single-sided strip of light is in the focal plane perpendicular to the laser's direction of propagation.

Piles of suggestions for what can be done with light
The researchers not only depend on the calculations of the theoreticians to prove the existence of the Moebius strip, which the human eye cannot resolve at the focal point. "In Erlangen, we recently developed a method for measuring electromagnetic fields with very high resolution," says Peter Banzer.

To this end, the researchers place a tiny gold sphere measuring a mere 82 nanometres in diameter onto a glass plate in the focal plane. A small fraction of the light that is transmitted through the glass plate is scattered by the tiny nanosphere.

"We can reconstruct the strength and the orientation of the electromagnetic field at any point in the focal point from the scattering pattern," explains Banzer. This requires the researchers to collect the scattered and non-scattered light using a further microscope objective lens and measure it with the aid of a CCD camera.

This optical field study is the first time it has been possible to experimentally detect the existence of Moebius strips formed by the polarisation of light. The measurements here look exactly as predicted by the theoretical considerations.

A result which indicates two things, according to Peter Banzer: "On the one hand, my colleague Thomas Bauer, who carried out a large part of this experimental work, has worked with very high precision and focused the laser light very accurately."

On the other hand, comparing the theory and the experiment shows how sensitive and accurate the method for analysing the fields is - an important finding from the work, but not the only one: "With the optical Moebius strip we have now demonstrated an effect the existence of which had not been clear until this point," says Gerd Leuchs, who headed the work as Director of the Max Planck Institute in Erlangen and professor at the FAU. "And we show that light can be used to create very complex structures."

The physicists will now continue their work with shaped light waves in different directions. "We want to see whether optical Moebius strips exist elsewhere," says Peter Banzer. Furthermore, his team and its cooperation partners want to test whether this optical structure is suitable for processing materials or as optical tweezers.

"And what's more, several theoreticians have already contacted me," says the physicist: "Now that it's possible to measure optical field distributions on the nanoscale with such accuracy, they've been able to produce piles of further suggestions as to what we can do with light."


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
Max-Planck-Gesellschaft
Powering The World in the 21st Century at Energy-Daily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








ENERGY TECH
Electrochromic polymers create broad color palette for sunglasses, windows
Athens GA (SPX) Feb 12, 2015
Artists, print designers and interior decorators have long had access to a broad palette of paint and ink colors for their work. Now, researchers have created a broad color palette of electrochromic polymers, materials that can be used for sunglasses, window tinting and other applications that rely on electrical current to produce color changes. By developing electrochromic polymer materia ... read more


ENERGY TECH
Application of laser microprobe technology to Apollo samples refines lunar impact history

NASA releases video of the far side of the Moon

US Issuing Licenses for Mineral Mining on Moon

LRO finds lunar hydrogen more abundant on Moon's pole-facing slopes

ENERGY TECH
The highest plume ever observed on Mars

Mars One cuts list of potential colonists to 100

Mystery Mars plume baffles scientists

Up, Up and Away! First Humans Chosen for Mission to Mars

ENERGY TECH
The ISS Menu: Mayo, Espressos, Booze? Cosmonauts Reveal Their Secrets

Sensors Detect Icing Conditions to Help Protect Airplanes

Industry: Risk aversion costs more than 'fast failure'

Boeing's Space Efforts to Be Managed by Newly Created Organization

ENERGY TECH
More Astronauts for China

China launches the FY-2 08 meteorological satellite successfully

China's Long March puts satellite in orbit on 200th launch

Countdown to China's new space programs begins

ENERGY TECH
Spacesuit woes haunt NASA ahead of crucial spacewalks

Russia Launches Fresh Fruit, Oxygen to Crew on ISS

Space Station 3-D Printed Items, Seedlings Return in the Belly of a Dragon

NASA preparing to reassemble International Space Station

ENERGY TECH
Moog offers "SoftRide" for enhanced spacecraft protection during launch

Russian-Ukrainian Satan Rocket to Launch South Korean Satellite as Planned

Leaders share messages, priorities at AFA Symposium

Soyuz Installed at Baikonur, Expected to Launch Wednesday

ENERGY TECH
Laser 'ruler' holds promise for hunting exoplanets

The mystery of cosmic oceans and dunes

Scientists predict earth-like planets around most stars

"Vulcan Planets" - Inside-Out Formation of Super-Earths

ENERGY TECH
Arachnid Rapunzel: Researchers spin spider silk proteins into artificial silk

Breakthrough may lead to industrial production of graphene devices

New design tool for metamaterials

New self-stretching material developed at University of Rochester




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.