Hightech Gründerfonds (HTGF) invests in the start-up Twenty-One Semiconductors

The spin-off from the University of Stuttgart produces semiconductor-based laser crystals for biomedical applications. With these crystals, laser modules can be realized in the yellow spectral range, which was previously difficult to access, significantly increasing the information content of measurements on cell and tissue samples.

The demand for laser modules with central wavelengths in the visible spectral range is growing continuously and is finding wide application in biomedicine in particular. In this field, highly specialized beam sources are used to analyze blood and tissue samples in order to test the efficacy of new drugs and develop more effective therapies against cellular diseases.

Laser radiation is used to excite fluorescent dye molecules, which attach themselves to certain cell components with the help of receptors, to glow. This characteristic glow provides information about the composition of the cell sample. By using laser modules with different wavelengths, i.e. colors, it is possible to excite a variety of different dyes and thus investigate a whole range of cell properties simultaneously. For this reason, modern analyzers house up to eight excitation lasers with different emission wavelengths.

Semiconductor diodes are typically used in red and blue laser modules. These have a high efficiency, are very compact and uncomplicated to handle. In the green and yellow spectral range, however, efficient laser diodes are not available due to the materials used, which is why most laser manufacturers rely on solid-state lasers there. In contrast to semiconductor diodes, these lasers are much more complex in their design and require the precise alignment of a large number of optical components as well as the exact temperature stabilization of the system. This makes them very expensive and complex to manufacture.

Over the past two years, the founders of 21S have developed a novel laser crystal based on the extensive research conducted at the Institute of Semiconductor Optics and Functional Interfaces at the University of Stuttgart, which can be used to generate visible laser radiation in a straightforward manner.