'Sandwich' effect unlocks low-cost laser material

MEH-PPV is a low-cost material that can be integrated with silicon chips, and researchers have sought to use the material to convert electricity into laser light for use in devices including optical amplifiers and chemical sensors.

However, attempts to do this have failed because the amount of electricity needed to generate laser light in MEH-PPV was so high that it caused the material to degrade.

Now researchers at North Carolina State University claim to have developed an inexpensive way to confine more light in the material, which lowers the energy threshold needed to produce focused laser light by 50 per cent.

According to the university, the researchers did this by sandwiching the MEH-PPV between two materials that have matching indices of refraction, efficiently reflecting light back into the MEH-PPV and preventing light from escaping. This results in lower thresholds for laser light.

‘This approach is fairly inexpensive and could also be easily scaled up for large-scale processing,’ said Dr Lewis Reynolds, a teaching associate professor of materials science and engineering at NC State and co-author of a paper describing the research.

The sandwich also makes the material more stable by limiting the MEH-PPV’s exposure to oxygen. This makes the material 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 Ph.D. student at NC State and lead author of the paper. ‘We’re working on that now.’

The paper, Enhancement of optical gain and amplified spontaneous emission due to waveguide geometry in the conjugated polymer poly[2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene]is published online in Applied Physics Letters. The paper was co-authored by Dr John Papanikolas of the University of North Carolina at Chapel Hill.