THE ABILITY to manipulate and control light is one of the foremost goals of modern optics. However, it is also something that nature perfected a long time ago. About 500 million years ago an evolutionary “big bang” took place, when animal life began to rapidly diversify. This so-called Cambrian explosion is thought to have been triggered when light became important in the behaviour of many animals. When it comes to highly advanced optical systems, it seems there is no more experienced an engineer than nature itself.
It is no wonder then that the optical engineers of today have started to keep a curious eye on natural optical systems. These systems offer inspiration for new ideas in optical design, and could provide shortcuts for developing advanced photonic systems, which one day it may even be possible to grow to order. Without doubt, uncovering nature’s optical secrets has been, and will continue to be, a spectacular journey.
Some of the most interesting optical systems in nature are hard to miss. They are often brightly coloured, metallic looking or strongly iridescent, and stand out from ordinary objects and surfaces that are coloured by pigmentation alone. In the 18th century Robert Hooke and Isaac Newton were among the first to form theories that explained the underlying physics of these systems. They correctly predicted that the iridescent colours of peacock feathers and silverfish scales resulted from their physical structure rather than pigmentation. This was a huge leap of understanding, considering that the means of seeing these structures would not be invented for a further two centuries.
Over the last 10 years or so the physics of 2-D and 3-D photonic crystals has been examined in great detail, and there is currently significant interest in optical technologies based on photonic structures. Synthetic photonic-crystal fibres – which were pioneered by Philip Russell and co-workers at the University of Bath in 1995 – could outperform even optical fibres in their efficiency in transporting light.
In the February issue of Physics World Pete Vukusic in the Thin Film Photonics Group in the School of Physics at Exeter University, UK describes this field in more detail.