High-Power Visible Spectrum Diode Lasers For Display And Medical Applications

By Andreas Unger, Bernd Köhler, and Jens Biesenbach

In this paper we report on the further progress of fiber coupled high power diode lasers in the visible spectral range with regard to beam quality and spectral characteristics. Improved beam shaping concepts allow coupling of red and blue diode lasers into smaller fibers. For medical applications beam sources with narrow wavelength distribution in the blue spectral region were developed. Modules up to 100W in a 400μm NA0.22 fiber were realized. Progress in manufacturing technologies allows for coupling of more than 25W into a 200μm NA0.22 fiber in the blue wavelength range.

Diode lasers in the visible spectral range are currently a highly active field of research. While the development of red and blue diode lasers is driven by the goal to replace arc lamps in cinema or home projectors and enable mobile projectors that can be incorporated into smartphones, the availability of high power diode lasers in the red and blue spectral region also enables other new applications. The discovery that blue light with wavelengths smaller than 450nm can be used to fight pathogens1 opens up markets for fiber coupled blue lasers in the medical area. Blue Lasers with a wavelength of 444nm can also be used as a pumping source for Pr3+ and enables the creation of several laser lines in the blue to red spectral range without frequency doubling2. On the other hand red lasers at wavelengths of ~638nm can also be used to several semiconductor and solid state lasers which is interesting e.g. for LIDAR applications. Of course the application for large venue and cinema projectors is still highly relevant, and it is expected that the first cinema projectors operating with laser light sources will be released in 2014 to public cinemas.