Some butterfly wings shimmer and shine, and an international team of researchers have discovered the secret behind this ability.
Researchers were able to break the limit of light resolution at the nanoscale and deliver a fundamental insight into how light and matter interact using a new technique which combines electronic excitation and optical detection.
They were able to explore the inside of a photonic crystal and study the confinement of light, revealing a greater understanding of how light interacts with matters to create iridescent phenomena – like the wings of butterflies.
“We were thrilled in the lab to observe the finer details of the photonic crystals that were simply inaccessible before,” said Dr Riccardo Sapienza from the Department of Physics at King’s College London. “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 team constructed an artificial two-dimensional photonic crystal, etching a hexagonal pattern of holes in a very thin silicon nitride membrane. Photonic crystals are nanostructures in which two materials with different refractive indices are arranged in a regular pattern – giving rise to unusual optical properties. The crystals inhibit light propagation for certain colours of light, which leads to strong reflection of those colours.
Researchers used a beam of electrons generated by an electron gun to cause the material to emit visible light. By scanning the beam, researchers can visualise the optical response of the nanostructure and reveal features 10 times smaller than ever before.
“It is fascinating to finally have an immediate view of the light in all its colours inside a photonic crystal,” said Professor Niek van Hulst of ICFO in Barcelona.
The research – published in Nature Materials – could lead to the development of enhanced biosensors for healthcare and more efficient solar cells and displays.