Plugging the holes of a polymer called MEH-PPV prevents light from leaking out, providing a low-cost way to enhance the material for use in photonic devices.

“Think of a garden hose. If it has holes in it, water springs out through a million tiny leaks,” said Dr. Lewis Reynolds, a teaching associate professor of materials science and engineering at North Carolina State University. “But if you can eliminate those leaks, you confine the water in the hose and improve the water pressure. We’ve plugged the holes that were allowing light to leak out of the MEH-PPV.”

Researchers have long sought to use the inexpensive polymer, which can be integrated with silicon chips, in devices such as optical amplifiers and chemical sensors to convert electricity into laser light. However, previous attempts have failed because the amount of electricity needed to generate laser light in MEH-PPV is so high that it causes the material to degrade.

Now Reynolds and colleagues have developed a low-cost way to confine more light in the polymer by sandwiching it between two materials that have matching indices of refraction, efficiently reflecting light back into the MEH-PPV and preventing light from escaping. This lowers by 50 percent the energy thresholds needed to produce focused laser light.

“This approach is fairly inexpensive and could also be easily scaled up for large-scale processing,” Reynolds said.

The “sandwich” also makes the material more stable: The MEH-PPV is less exposed to oxygen and less subject to degradation due to photo-oxidation, which occurs when materials are exposed to both light and oxygen.

“This is a meaningful step forward for low-cost fabrication of these devices, but further optimization is required,” said Dr. Zach Lampert, a former doctoral student at NC State and lead author of the paper. “We’re working on that now.”

The study was published online in Applied Physics Letters (doi: 10.1063/1.4793422).  

For more information, visit: www.ncsu.edu