Birch leaves and peanuts turned into advanced laser technology

The results have been published in the scientific journal Nanophotonics and show how a so-called random laser can be made entirely from biological materials.

Jia Wang, Department of Physics.

ImageHans Karlsson

“Our study shows that it is possible to create advanced optical technology in a simple way using only local, renewable materials,” says Jia Wang, Associate Professor at the Department of Physics, Umeå University, and one of the authors of the study.

A random laser is a type of laser in which light scatters many times inside a disordered material before emerging as a focused beam. It holds great promise for applications such as medical imaging and early disease detection, and has therefore attracted significant research attention. However, conventional random laser materials are often toxic, or expensive and complex to produce.

Carbon dots from birch leaves

Jia Wang and her collaborators created their laser using two common natural materials: birch leaves and peanut kernels. They made nanometre-scale carbon dots from the birch leaves to serve as the gain medium and cut peanut kernels into small cubes whose rough and irregular surfaces help trap and scatter light.

Instead of relying on complex technology, the natural microstructure of the peanut kernel does the job on its own

The laser itself is still powered by an external light source, but the functional parts that scatter and amplify the light are made entirely from biomaterials.

“The synthesis of the carbon dots is simple and straightforward, essentially a one-step pressure-cooking process,” explains Jia Wang. “Instead of relying on complex technology, the natural microstructure of the peanut kernel does the job on its own," says Jia Wang.

Could be developed into an optical tag

The researchers tested how much energy was required to make the laser emit light, and the results showed that it performs just as well as artificially engineered lasers.

Upper: The biomaterial-based random laser when activated.
Lower: The same laser seen in daylight.

ImageZhihao Huang

“The potential of this biomaterial-based random laser extends beyond bioimaging and diagnostics. Given its low cost, renewability, and safety, it could also be developed into an optical tag for authenticating high-value documents, luxury goods, and electronic devices,” says Jia Wang.

Jia Wang’s research group has long been working on harnessing local, renewable resources for new technologies. Two years ago, they published a study demonstrating how birch leaves collected on Umeå University’s campus can be used to produce organic semiconductors – materials found in thin TV and mobile phone displays.