Scientists shed light on glowing materials

Aug 20, 2012

Researchers at King's College London, in collaboration with European research institutes ICFO (Barcelona) and AMOLF (Amsterdam), have succeeded in mapping how light behaves in complex photonic materials inspired by nature, like iridescent butterfly wings. Scientists have broken the limit of light resolution at the nanoscale and delivered a fundamental insight into how light and matter interact, which could lead to the development of enhanced bio-sensors for healthcare and more efficient solar cells and displays.

of at the nanoscale have always been limited by the resolution of the , but researchers were able to break this limit using a new technique which combines electronic excitation and , to explore the inside of a photonic crystal and study the confinement of light. Working with a spatial resolution of 30 nanometers, scientists examined the structures at a resolution more than ten times smaller than the for light, revealing a greater understanding of how light interacts with matter to create, for example, the visible iridescence phenomena observed in nature on the wings of butterflies.

Dr Riccardo Sapienza, from the Department of Physics at King's, said: 'We were thrilled in the lab to observe the finer details of the that were simply inaccessible before. This is very important as it allows scientists to test optical theories to a new level of accuracy, fully characterise new optical materials and test new optical devices.'

The collaborative research has been published in the journal .

The team constructed an artificial two-dimensional photonic crystal by etching a of holes in a very thin membrane. Photonic crystals are nanostructures in which two materials with different refractive indices are arranged in a regular pattern, giving rise to exotic optical properties. Natural photonic crystals can be found in certain species of butterflies, birds and beetles as well as in opal gemstones where they give rise to beautiful shimmering colours.

The photonic crystal inhibits light propagation for certain colours of light, which leads to strong reflection of those colours, as observed when such materials 'catch the light'. By leaving out one hole, a very small cavity can be defined where the surrounding crystal acts as a mirror for the light, making it possible to strongly confine it within a so-called 'crystal defect cavity'.

The scientists based their research methods on a technique used in geology, called cathodoluminescence, whereby a beam of electrons is generated by an electron gun and impacted on a luminescent material, causing the material to emit visible light. Professor Albert Polman and his group in AMOLF modified this technique to access nanophotonics materials. He said: 'In the past few years we have worked hard with several technicians and researchers to develop and refine this new instrument.'

Dr Sapienza said: 'Each time a single electron from the electron gun reaches the sample surface it generates a burst of light as if we had placed a fluorescent molecule at the impact location. Scanning the electron beam we can visualise the optical response of the nanostructure revealing features 10 times smaller than ever done before.'

Professor Niek van Hulst, ICFO, said: 'It is fascinating to finally have an immediate view of the light in all its colours inside a photonic crystal. For years we have been struggling with scanning near-field probes and positioning of nano-light-sources. Now the scanning e-beam provides a local broad-band dipolar light source that readily maps all localised fields inside a photonic crystal cavity.'

With major advances in nanofabrication techniques it has become possible to construct artificial photonic crystals with optical properties that can be accurately engineered. These structures can be used to make high-quality nanoscale optical waveguides and cavities, which are important in telecommunication and sensing applications.

Dr Sapienza said: 'Our research provides a fundamental insight into light at the nanoscale and, in particular, helps in understanding how light and matter interact. This is the key to advance nanophotonic science and it can be useful to design novel optical devices like enhanced bio-sensors for healthcare, more efficient and displays, or novel quantum optics and information technologies.'

Explore further: Engineers make sound loud enough to bend light on a computer chip

Related Stories

Optical surface states in magnetophotonic crystals

Oct 26, 2010

Using state of the art microfabrication technology to create periodic structures with high accuracy, Dr Baryshev and colleagues at the Toyohashi University of Technology, Japan, report the existence of so-called ...

Futuristic computing designs inside beetle scales

Sep 30, 2010

(PhysOrg.com) -- Though it began as a science fair project involving a shiny Brazilian beetle, Lauren Richey’s research may advance the pursuit of ultra-fast computers that manipulate light rather than electricity.

Fabricating 3D Photonic Crystals

Jan 21, 2009

(PhysOrg.com) -- “In photonic crystals, the ability to control the structure of a material in full three dimensional space, allows you to control the way that light flows through it,” John Rogers tells PhysOrg.com. “Thi ...

Green light from Silicon

Apr 15, 2009

(PhysOrg.com) -- Researchers at the University of St Andrews have made a surprise discovery that the material at the heart of the microelectronics industry can emit green light.

Sharpening the focus of microscopes

Dec 02, 2011

A new advanced imaging scheme—with a resolution ten times better than that of its counterparts to date—can resolve objects as small as atoms1. Previously, the maximum resolution of optical instruments, ...

Recommended for you

New largest number factored on a quantum device is 56,153

10 hours ago

(Phys.org)—Researchers have set a new record for the quantum factorization of the largest number to date, 56,153, smashing the previous record of 143 that was set in 2012. They have shown that the exact same room-t ...

Scientists film magnetic memory in super slow-motion

13 hours ago

Researchers at DESY have used high-speed photography to film one of the candidates for the magnetic data storage devices of the future in action. The film was taken using an X-ray microscope and shows magnetic ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.