The first controllable random laser based on paper-based ceramics

The team led by Professor Cordt Zollfrank of the TUM worked with physicists at the University of Rome to create the first controlled random laser based on cellulose paper at the Straubing Science Center. Based on this, the team showed how naturally-occurring structures can be adapted to technical applications. Therefore, it is no longer necessary to manually prepare the material into a disordered structure, but to replace it with a natural material.

Biomimetic material synthesis is one of the areas of research for the Biopolymer Composites Board at the Technische Universitat Technische Universitat Technische Universiteit Munich. It uses templates of natural and biological materials to develop new materials and technologies. The latest issue of Advanced Optical Materials presents a basic study done by a joint team of the Straubing Science Center and the University of Rome, according to scientist Daniel Van Opdenbosch, Ph.D., who succeeded in "bringing a biological Structure is used as a template for a technical random lasers ".

The team used traditional laboratory filter paper as a structural template because of its long fiber and stable structure.

There are two components that are indispensable to lasers: First, there is a need for a gain medium for optical amplification. Second, there is a need for a structure that holds light in the medium. Classical lasers use mirrors to guide light and spread it in a single direction in a directional and uniform manner. This also happens uniformly in the microstructure of a random laser, but in different directions. Although the development of stochastic laser is still in its infancy, in the future, it may bring lower cost of production. This is because stochastic lasers have some advantages, such as their directional independence and their multiple colors, which list only a few of the benefits.

Disordered structures deflect light in all directions

"Random lasers are based on the assumption that there is a certain degree of confusion in the internal structure," explained Van Opdenbosch. Therefore, the light inside the random laser will scatter at all angles and along random paths, which is determined by an irregular structure inside the medium. The team, led by Prof. Zollfrank from the Bio-Polymer Committee at Straubing Science Center, uses conventional laboratory filter paper as a structural template. "Because of its long fibers and the resulting stable structure, we think it is well suited for this purpose," said Van Opdenbosch.

In the laboratory, these filters were impregnated with an organic metal compound, tetraethyl ortho titanate. When it is dried and the cellulose is burned down at 500 degrees Celsius, it leaves ceramic titanium dioxide as a residue - the same substance normally used to prevent sunburn in sunscreens. "This effect in sunscreens is based on the intense light scattering effect of titanium dioxide," said Van Opdenbosch. "We also apply this effect to our stochastic lasers." "Our lasers" are "random "Because light scattered in different directions due to the biological structure of the filter paper in the lab can also be scattered in the opposite direction," he added, explaining the principle.

After all, random lasers are not completely random

Despite its random nature, the lightwave can still be controlled, as Daniel Van Opdenbosch and Cordt Zollfrank have collaborated with, as the team headed by Claudio Conti of the Complex Systems Institute at the University of Rome discovered. With the help of a spectrometer, they can distinguish the different laser wavelengths generated in the material and position them individually.

Van Opdenbosch described the process: "The test setup used to draw the sample map consists of an energy-adjustable green laser, a microscope lens, and a mobile station that moves the sample so that our colleagues can determine if they are different Different energy levels and different laser radiation radiated by different regions of the material. "Within this analyzed light, it is possible to configure the laser in any number of paths and determine the direction and intensity of its radiation.

This knowledge makes some of the potential practical application a reality. "For example, this material can be used as a micro-switch or probe to detect structural changes," said Van Opdenbosch.