Folding and cutting thin metal films could enable microchip-based 3-D optical devices.
Nanokirigami has taken off as a field of research in the last few years; the approach is based on the ancient arts of origami (making 3-D shapes by folding paper) and kirigami (which allows cutting as well as folding) but applied to flat materials at the nanoscale, measured in billionths of a meter.
Now, researchers at MIT and in China have for the first time applied this approach to the creation of nanodevices to manipulate light, potentially opening up new possibilities for research and, ultimately, the creation of new light-based communications, detection, or computational devices.
The findings are described today in the journal Science Advances, in a paper by MIT professor of mechanical engineering Nicholas X Fang and five others. Using methods based on standard microchip manufacturing technology, Fang and his team used a focused ion beam to make a precise pattern of slits in a metal foil just a few tens of nanometers thick. The process causes the foil to bend and twist itself into a complex three-dimensional shape capable of selectively filtering out light with a particular polarization.
Previous attempts to create functional kirigami devices have used more complicated fabrication methods that require a series of folding steps and have been primarily aimed at mechanical rather than optical functions, Fang says. The new nanodevices, by contrast, can be formed in a single folding step and could be used to perform a number of different optical functions.
For these initial proof-of-concept devices, the team produced a nanomechanical equivalent of specialized dichroic filters that can filter out circularly polarized light that is either “right-handed” or “left-handed.” To do so, they created a pattern just a few hundred nanometers across in the thin metal foil; the result resembles pinwheel blades, with a twist in one direction that selects the corresponding twist of light.
thumbnail courtesy of mit.edu