48

nanotimes News in Brief Metamaterials //

Silver Nanostructures in a Polymer Matrix © Based on Material by Caroline Perry / Harvard University

W

orking at a scale applicable to infrared light, a Harvard University team has used extremely

short and powerful laser pulses to create three- dimensional patterns of tiny silver dots within a material. Those suspended metal dots are essential for building futuristic devices like invisibility cloaks. The new fabrication process advances nanoscale metal lithography into three dimensions – and does it at a resolution high enough to be practical for meta- materials.

“If you want a bulk metamaterial for visible and inf- rared light, you need to embed particles of silver or gold inside a dielectric, and you need to do it in 3D, with high resolution,” says lead author Kevin Vora, a graduate student at the Harvard School of Enginee- ring and Applied Sciences (SEAS).

Vora works in the laboratory of Eric Mazur, Balkanski Professor of Physics and Applied Physics at SEAS. For decades, Mazur has been using a piece of equipment called a femtosecond laser to investigate how very tightly focused, powerful bursts of light can change the electrical, optical, and physical properties of a material.

When a conventional laser shines on a transparent material, the light passes straight through, with slight refraction. The femtosecond laser is special because

The experimental setup in Prof. Eric Mazur‘s laser labo- ratory at Harvard. Using femtosecond lasers, Mazur and colleagues have developed a new nanofabrication process for use in creating metamaterials. © Eliza Grinnell, Harvard SEAS.

“This work demonstrates that we can create silver dots that are disconnected in x, y, and z.

There’s no other technique that feasibly allows you to do that. Being able to make patterns of nanostructures in 3D is a very big step towards the goal of making bulk metamaterials.

” Kevin Vora

12-02 :: February/March 2012