Plastic Laser Diodes - One Step Closer to Reality

Typical laser diodes generally found in optical storing devices such as Blu-ray, DVD and CD players are currently being fabricated out of inorganic semiconductors like gallium arsenide, gallium nitride and other semiconductor alloys related to them. Now, researchers have demonstrated a class of plastic semiconductor materials that may be used in the future to manufacture electrically-powered plastic laser diodes.

A semiconductor is a material that in certain conditions behaves like either a conductor or an insulator. Light emitting semiconductor materials like gallium arsenide produce light emissions by combining positive and negative electric charges inside them. The emitted light is then amplified several times by bouncing light inside the material until it bears enough energy to penetrate one side and exit into the medium in the form of a narrow, intense and directional spectral emission, called laser beam.

In the last decades the research in the field of light emitting semiconductors has steadily but surely shifted into the realm of organic materials, resulting in the development of organic light emitting diodes, field effect transistors and even photodiodes. Practically, plastic laser diodes remained the only devices that haven't been yet demonstrated.

This is mostly because researchers believed that plastic semiconductors for laser diodes are unable to support large current intensities to generate an efficient light emission that would then be converted to a laser beam. The new plastic semiconductor developed by the Sumitomo Chemical Company is said to be 200 times better in carrying electric charges than the previous most efficient material, it emits blue light and it could be used to create the next generation of laser diodes.

"This study is a real breakthrough. In the past designing polymers for electronic and optoelectronic devices often involved maximising one key property in a material at a time. When people tried to develop plastic semiconductors for laser diode use, they found that optimising the material's charge transporting properties had a detrimental effect on its ability to efficiently emit light, and vice versa", says Professor Donal Bradley of Imperial's Department of Physics who was also leader of the study.

"The modifications made to the PFO structure have allowed us to convincingly overcome this perceived incompatibility and they suggest that plastic laser diodes might now be a realistic possibility", explained Dr Paul Stavrinou, co-author of the study.

The new plastic semiconductor, besides enabling the manufacturing of plastic laser diodes at low cost and providing easier integration solutions, may also be used to create laser diodes covering the full visible spectrum of light and could allow standard plastics to be used as waveguides for light and in manufacturing fiber optics.

The research team argues that the future laser diodes made out of the material they have developed may generate light emissions covering the spectrum all the way from near ultraviolet to near infrared.