A software tool developed at Sandia National Lab lets users design science-fiction-like materials with the same efficiency architects have in drafting building plans. The software, dubbed Mirage, is the first inverse-design program for assembling for optical metamaterials. Inverse design refers to the fact users start by describing the result they want, and the software fills in the steps to get there. This takes much of the guesswork out of engineering as-yet-theoretical technologies like ultra-compact, high-performance cameras and cloaking armor that could make wearers invisible to detection.
Sandia uses Mirage in its R&D programs and released a test version to select collaborators last year. Now, researchers working on government metamaterial projects can request a license at no cost.
Manmade optical metamaterials have been touted for more than a decade for their ability to manipulate light in extraordinary ways. In theory, satellite imaging and interstellar telescopes could be dramatically smaller with metamaterial lenses 100 times thinner than conventional ones. Or, the technology could someday lead to cloaking materials that deflect light around them, rendering objects impossible to see.
Mirage simplifies and automates the design process for materials that would be necessary for those devices. Researchers interested in a copy are invited to contact Sandia for more information. To be eligible for one, recipients must first have a valid research contract with the U.S. government. Mirage runs on Windows and can be configured to operate on laptop, desktop, and multicore machines.
The field of optical metamaterials has so far struggled to deliver on all its promises of revolutionizing optics. One difficulty for engineers has been that metamaterials are made of tiny building blocks, called meta-atoms, which can be designed in countless variations. A certain shape might bend light. Change that shape, the size, the spacing or material, and it might amplify the effect, diminish it, or cause something entirely different to happen—like twist the light one direction or another or change its intensity or color.
“Predicting what the properties will be has been hard to determine until now,” says DARPA program manager Mike Fiddy. The agency funded the software’s development. Other software simulates what meta-atoms will do to light, but that only lets researchers use intuition to experiment with different designs until they stumble upon or tediously work out the behaviors they want.
Despite the challenge, some researchers have created imaginative metamaterial devices. For example, one Sandia engineer invented a device that converts heat to electricity, potentially for more fuel-efficient engines. A new light-mixing method could lead to a new, changeable, multicolored light source, which could accelerate all kinds of research from archeology to biomedicine.
But on the whole, says Sandia scientist Ihab El-Kady, the metamaterial enterprise has needed a boost.
“We cannot possibly solve this problem by trial and error,” says El-Kady, who conceived Mirage. “Instead, we could do the opposite. We could say: ‘Here is the behavior I want. Now tell me what the metamaterial looks like.’”
No tool used this inverse-design approach. So, El-Kady and his team at Sandia’s National Security Photonics Center built one.
Mirage lets users start by telling it the optical property they want—how their metamaterial needs to interact with light—and their starting materials. Mirage generates designs that match those criteria from a library of more than 100 templates. Or, users can draw their own designs and the program will check them for errors.
“A more systematic approach for designing metamaterials should greatly accelerate their adoption in various application areas and eliminate the more commonly used intuition-based approaches, says Fiddy.
“Mirage is an all-in-one tool,” El-Kady explains. “Not only does it tell you what the metamaterial looks like, it lets you explore various configurations, simulate the material, validate the chosen behavior, visualize its response, and improve its behavior within your fabrication constraints.”
On top of that, Mirage includes algorithms that help researchers get the best performance from their inventions.
For example, the team created a material that can mix two lasers to produce 11 colors at once, including infrared and ultraviolet light. Potentially, this could be developed into tunable lasers that replace single-color ones. But some of those colors are too dim to be useful, so the software helps them explore ways to brighten the output.
If the initial launch is successful, Sandia plans to develop a second version of Mirage, tentatively called Mirage Elite, that would automatically morph meta-atoms into bizarre and outlandish shapes in the hunt for undiscovered behaviors.
