Researchers have demonstrated that a long-elusive kind of laser diode based on organic semiconductors is indeed possible, paving the way for the further expansion of lasers in applications such as biosensing, displays, healthcare, and optical communications.

Schematic representation of an organic semiconductor laser diode producing blue laser emission under electrical excitation. (Credit: Kyushu University)

Long considered a holy grail in the area of light-emitting devices, organic laser diodes use carbon-based organic materials to emit light instead of the inorganic semiconductors, such as gallium arsenide and gallium nitride, used in traditional devices.

Organic laser diodes produce a much purer light enabling additional applications, but they require currents that are magnitudes higher than those used in OLEDs to achieve the lasing process. These extreme conditions caused previously studied devices to break down well before lasing could be observed.

To overcome obstacles, the group used a highly efficient organic light-emitting material (BSBCz) with a relatively low resistance to electricity and a low amount of losses — even when injected with large amounts of electricity. But having the right material alone was not enough.

They also designed a device structure with a grid of insulating material on top of one of the electrodes used to inject electricity into the organic thin films. Such grids — called distributed feedback structures — are known to produce the optical effects required for lasing, but the researchers took it one step farther.

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