The strange field of metamaterials offers some weird optical effects, like cloaking and superlenses. Recently, two breakthroughs in the field, involving programmable materials and gold nano-corkscrews, just made this exotic nano-stuff a little more practical, and maybe even stranger.
Metamaterials are materials engineered to do things nature didn't intend them to do. (We've covered them before.) The most commonly built kind of metamaterials are "optically active" metamaterials, or materials that make light behave in strange ways. They do this by making light bend around tiny folds or dip into nano-sized wells.
The strange interactions between light and metamaterials come with limitations, though. For any seriously strong light effects you traditionally need a lot of this material, something like a hundred wavelengths thick. But researcher Justyna Gansel and a team of scientists have devised a way to get strong optic effects with a lot less metamaterial.
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As revealed in their paper published in Science, the secret is actually tiny gold corkscrews. The team used lasers to carve these tiny nano-scale coils out of gold, and the resulting array of golden pigtails is their secret for strong optical effects. What took a hundred wavelengths' thickness of material to have the desired effect before now takes only one wavelength's thickness.
In practical terms (and the field of metamaterials is getting closer and closer to being practical), this means that your theoretical invisibility device just went from being an invisibility wall to an invisibility fabric.
Another major limitation on the metamaterial field is tunability. A material built to manipulate a certain wavelength of light can't easily do the same for another wavelength. In other words, a polarizer for blue light can't easily polarize red light.
A team headed by Tom Driscoll has developed a solution, also published in Science. They have devised a type of metamaterial that is not only tunable (it can be warped and changed to serve different wavelengths and functions), but it can remember its different states. Going back to the polarizer example, this would mean that your red light polarizer could switch easily between red and blue light, and any number of other states.
When taken together, these two discoveries pave an interesting path. Metamaterials have gone from custom-made, one-use, bulky set-ups to versatile, programmable, and best of all very thin materials. And the path that these discoveries delineate leads towards increasingly strange and impressive metamaterials.
Gold Helix Photonic Metamaterial as Broadband Circular Polarizer [Science]
Memory Metamaterials [Science]