Properties of diode laser pumps for high-power solid-state lasers

Diode lasers used to pump high average power solid-state lasers typically have broad spectral width so that most of the pump light is not at the peak of the gain medium's absorption feature. However, the long absorption length in these lasers enables even weakly absorbed light to pump efficiently. The result is that high absorption efficiency and improved pump distribution uniformity are possible when using realistic pump diodes. In addition, both quantities are nearly independent of the pump center wavelength.

Diode laser pumped solid-state lasers have been considered, developed and sold for a number of years. In general, these have been either small, low power lasers or side pumped rod-shaped lasers with short paths available in which the pump light could be absorbed. As a result, there has been a concentrated effort to prepare pump sources with narrow lasing spectra or find gain media with wide absorption features. In this paper, we evaluate the use of realistic diode laser pump sources in high average power solid-state lasers. In particular, we examine the results of edge pumping [1] neodymium or ytterbium doped yttrium aluminum garnet (Nd:YAG or Yb:YAG) slab-shaped lasers capable of several kilowatts of output power. The conclusion we reach, that high efficiency and good uniformity are possible using broad spectrum pump diode sources, are applicable to other high average power lasers with long absorption paths such as edge pumped disks and fiber lasers. Our results also provide guidance to diode laser and diode array manufacturers supplying pump sources for high average power lasers.