Butterfly inspires beam-splitting nanotechnology

Three-dimensional nanostructures that create the vibrant green in a butterfly wing have inspired researchers to develop a photonic crystal that could overcome bandwidth bottlenecks in high-speed optical communication.

The researchers, from Swinburne University of Technology in Australia and Friedrich-Alexander Universität Erlangen-Nürnberg in Germany, mimicked the microscopic structures in the butterfly wing and developed a crystal that can split left and right circularly polarised light.

The crystal design was inspired by the Callophrys rubi butterfly, also known as the green hairstreak. This butterfly has three-dimensional nanostructures in its wings which give them their vibrant green colour. Other insects also have nanostructures that provide colour, but the Callophrys rubi has one important difference.

“This butterfly’s wing contains an immense array of interconnected nanoscale coiled springs that form a unique optical material. We used this concept to develop our photonic crystal device,” Swinburne PhD graduate Dr Mark Turner said.

The crystal nanodevice, which is smaller than the width of a human hair, has properties that don’t exist in naturally occurring crystals, specifically the ability to work with circular polarisation.

Using three-dimensional laser nanotechnology, the Swinburne researchers created a miniature photonic crystal that contains over 750,000 tiny polymer nanorods.

The crystal acts like a miniature polarising beamsplitter, similar to a device invented by Scottish scientist William Nicol in 1828. Polarising beamsplitters used in modern technology - such as telecommunications, microscopy and multimedia - are built from naturally occurring crystals, which work for linearly polarised light but not circularly polarised light.

“We believe we have created the first nanoscale photonic crystal chiral beamsplitter,” said Professor Min Gu, director of the Centre for Micro-Photonics at Swinburne.

“It has the potential to become a useful component for developing integrated photonic circuits that play an important role in optical communications, imaging, computing and sensing.

“The technology offers new possibilities for steering light in nanophotonic devices and takes us a step closer towards developing optical chips that could overcome the bandwidth bottleneck for ultrahigh-speed optical networks.”

Dr Turner is now working in California’s Silicon Valley to develop and commercialise new photonic technologies for real-world applications.

The project is part of the Centre for Excellence for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), funded by the Australian Research Council under the Centres of Excellence Program, with further support from seven constituent universities and 15 partner investigators. Dr Turner’s PhD project was also partly supported by the Australian Cooperative Research Centre for Polymers.

The research has been published in the journal Nature Photonics.