Time-multiplexing of high power laser diodes yields a high brilliance laser beam

Our work deals with a new approach to improve the beam quality of diode lasers, which is still insufficient for many applications. We propose time-multiplexing, where several pulsed laser diode beams are guided onto a common optical path. This allows to superpose the power of the diodes while maintaining the beam parameter product of a single laser diode. Pulsed operation of continuous wave laser diodes was shown to be possible up to pulse enhancement factors often provided that pulse duration is <300 ns. We use a fast digital optical multiplexer built up by a cascade of binary optical switches. For the latter we use a polarization switch (voltage-driven LiNbO₃-crystal) followed by a polarization filter, which allows addressing of two optical paths. Instead of direct on/off-switching we drive the crystals with a harmonic voltage course to avoid ringing caused by piezoelectricity. Up to now an optical power of 10.1 W was generated, 13 W are expected with some improvements. With the use of new 8 W laser diodes even the generation of 25 W will be possible.