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 accu
|Contact: Katherine Barnes|
King's College London