By carefully directing pulses of laser light, it is therefore possible to create continuous paths out of the polymer material. Then, after the researchers rinse out the remaining monomer, they fill the voids between the beads and the polymer material with a silicon-based material using a process called chemical vapor deposition. The entire structure is then bathed in hydrofluoric acid to dissolve all but the silicon.
What’s left is a solid structure of silicon with a network of waveguides within it, says Braun.
In the current issue of Nature Photonics, the group reports its findings and shows that by starting off with beads that are 725 nanometers in diameter, it is possible to create waveguides for a narrow band of wavelengths in the near-infrared range. This is potentially extremely useful, since this is the range that is currently employed for most optical communications, says Braun.
The work is more of an evolution than a revolution, says Johnson. And he notes that while Braun’s structures are not yet useful for making working devices, they are an important first step toward creating more complex and functional optical devices.