Researchers have created the first organic semiconductor laser to operate without the need for a separate light source

OLED is located at the top and is formed by an organic layer between the contacts. Apply voltage to it, inject charge and generate light, which in turn excites organic laser. Organic lasers contain a grating that can generate feedback and diffract some of the laser out of the structure.

Organic laser
Researchers have created the first organic semiconductor laser to operate without the need for a separate light source, which has been proven to be extremely challenging.
The new all electric laser is more compact than previous versions and operates in the visible light region of the electromagnetic spectrum, making it suitable for sensing, sensing, and spectroscopic applications.

A laser works by reflecting light back and forth, typically in an optical cavity containing a gain medium placed between two mirrors. When light is reflected between mirrors, the gain medium amplifies it, stimulating more light emission and producing coherent beams with a very narrow spectral range.

In 1992, the first organic laser was introduced. However, it uses a separate light source to drive its gain medium, which makes the design complex and limits its application. Since then, researchers have been trying to find a way to manufacture an organic laser that only uses an electric field to drive it.

Due to the work of Kou Yoshida and his colleagues at the University of St. Andrews in Scotland, this 30-year exploration has just reached its destination.

world record
There are two main strategies for designing electrically driven organic lasers. The first method is to place electrical contacts in an organic gain medium and inject charges through them. However, this is difficult to achieve because the injected charge absorbs light through the material's emission spectrum through the so-called triplet state. In addition, the contacts themselves also absorb light.
That's why Yoshida chose another approach: keeping charges, triplets, and contacts at a distance from the gain medium of the laser in space.

This is not an easy task either, as it means manufacturing a pulsed blue organic light-emitting diode with a light output intensity that should break world records, allowing it to trigger gain media and save additional light sources.

"In order to manufacture this device, we initially manufactured OLED and laser cavities separately, and then transferred OLED to the surface of the laser waveguide," Professor Ifor Samuel explained. The careful integration of these two parts is crucial for the gain medium to obtain strong electroluminescence generated inside OLED.

In order to complete the project, the team used diffraction gratings on thin film lasers to provide distributed feedback of laser emission in the thin film plane, while also diffracting the outgoing laser beam from the surface.

A slowly accelerating technology
Organic semiconductor devices are widely considered a "slow" technology because the charge mobility in organic materials is usually several orders of magnitude lower than that in crystalline silicon or III-V group semiconductors. But this innovation may start to change this perception and expand the scope of use of organic lasers.

As for the application, researchers claim that the new all electric organic semiconductor laser can be easily integrated into medical devices used in offices - various light based detection and spectroscopy devices for diagnosing diseases or monitoring symptoms.

Source: Laser Net