(July 17, 2015) A
single drop of blood is teeming with microorganisms—imagine if we could see
them, and even nanometer-sized viruses, with the naked eye. That’s a real
possibility with what scientists call a “perfect lens.” The lens hasn’t been
created yet, but it is a theoretical perfected optical lens made out of
metamaterials, which are engineered to change the way the materials interact
with light.
While a perfect lens—and the metamaterials it’s made of—is
almost perfect, it’s not foolproof. As the field of research expanded in the
past 15 years, more and more challenges arose.
Now, researchers at Michigan Technological University have
found a way to possibly solve one of the biggest challenges, getting light
waves to pass through the lens without getting consumed. The journal Physical
Review Letters published their study this July, a continuation of work done by
Durdu Güney, a professor of electrical and computer engineering at Michigan
Tech.
Güney worked alongside Mehdi Sadatgol, a PhD candidate at
Michigan Tech, and Sahin Kaya Özdemir and Lan Yang, both at the Department of
Electrical and Systems Engineering of Washington University in St. Louis. As
the team writes in their paper, “These findings open the possibility of
reviving the early dreams of making ‘magical’ metamaterials from scratch.”
The Promise of
Metamaterials
Metamaterials are often based on natural materials but can
be altered to have completely different optical properties. Metamaterials go
beyond the limits of natural materials such as glass, plastic, metal or wood.
To do that, the bases used for making a metamaterial—like the thin silver films
Güney’s group uses—are tweaked at the subwavelength scale so that light waves
interact with the material in new ways. While no one has created a perfect lens
yet, the metal base Güney tests would look more like a traditional glass lens;
light would pass through instead of reflecting off the metal.
“Aluminum and silver are the best choices so far in the
visible light spectrum, not just for a perfect lens but all metamaterials,”
Güney says, explaining that metamaterials have been successfully created with
these metals, although they still tend to absorb light waves. “Loss—or the
undesired absorption of light—is good in solar cells, but bad in a lens because
it deteriorates the waves,” he explains.
The solution for a sharper image then is to offer up a
sacrificial light wave.