Cracks are generally not welcome in car windows, glasses and other surfaces, but Dogru-Yuksel et al. show they could crack a light-emitting material and transform that into a random laser. While most random lasers have omnidirectional emission, cracks can reflect light back and forth and produce directional laser light.
The researchers were doing biomaterial laser experiments by using fluorescent proteins and, surprisingly, saw some laser emission from the cracks. After investigation, they understood the sidewalls were the scatterers, which diffused reflection and generated laser emission.
“This work is adaptable to a wide variety of materials,” said author Sedat Nizamoglu,. “Therefore, this study introduces a novel form of cracks to be used as lasers.”
In general, obtaining laser emission is a difficult task, in which mirrors need to be aligned in parallel. As light is reflected through the mirrors, it bounces back and forth between them, interfering with itself and increasing its energy in an excited dye medium. Eventually, the energy leaves the mirrors as the laser emission.
The researchers found that while the self-assembled side walls in their experiment were not parallel, the reflected light oscillated back and forth between the cracked side walls and generated laser light, creating what is called a random laser.
The researchers demonstrated fluorescent proteins extracted by genetically encoded bacteria can be used for random lasers. Hence, a wide variety of biomaterials, such as biopolymers, proteins and vitamins, can also become new random lasers, which can be also interfaced with living cells for light-generation from cellular environments and novel biosensing approaches.
Source: “High-Q, directional and self-assembled random laser emission using spatially localized feedback via cracks,” by Itir Bakis Dogru-Yuksel, Mertcan Han, Gregor Pirnat, Emir Salih Magden, Erkan Senses, Matjaž Humar, and Sedat Nizamoglu, APL Photonics (2020). The article can be accessed at https://doi.org/10.1063/5.0020528.
