Researchers from Kyushu University have demonstrated that organic laser diodes using carbon-based organic materials are possible.
The organic laser diodes could lead to further expansion for laser applications such as biosensing, displays, healthcare, and optical communications.
The difficulty of realising an organic laser diode
Atula S. D. Sandanayaka, lead author on the paper, commented: “I think that many people in the community were doubting whether we would actually one day see the realization of an organic laser diode, but by slowing chipping away at the various performance limitations with improved materials and new device structures, we finally did it.”
The injection of a large amount of electrical current into the organic layers is a critical step in lasing because it achieves a condition called population inversion. However, since many organic materials are resistant to electricity, it is difficult to get enough electrical charge in the materials before they heat up and burn out. Alongside this, a variety of loss processes are inherent to most organic materials and devices operating under high currents, which lowers efficiency and pushes the necessary cost up higher.
The leader of the research group, Prof. Chihaya Adachi, explained: “By optimising these grids, we could not only obtain the desired optical properties but also control the flow of electricity in the devices and minimize the amount of electricity required to observe lasing from the organic thin film.”
The right material and a new device structure
The team used BSBCz, a highly efficient organic light-emitting material which has a relatively low electricity resistance and a low amount of losses even when injecting with large amounts of electrical currents. They also used a device structure which was made by a grid of insulating material, called a distributed feed back structure, on top of one of the electrodes to inject electricity into organic thin films.