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Peak CW optical power from single 1-cm diode laser bars is advancing rapidly across all commercial wavelengths and
the available range of emission wavelengths also continues to increase. Both high efficiency ~ 50% and > 100-W power
InP-based CW bars have been available in bar format around 1500-nm for some time, as required for eye-safe
illuminators and for pumping Er-YAG crystals. There is increasing demand for sources at longer wavelengths.
Specifically, 1900-nm sources can be used to pump Holmium doped YAG crystals, to produce 2100-nm emission.
Emission near 2100-nm is attractive for free-space communications and range-finding applications as the atmosphere
has little absorption at this wavelength. Diode lasers that emit at 2100-nm could eliminate the need for the use of a
solid-state laser system, at significant cost savings. 2100-nm sources can also be used as pump sources for Thulium
doped solid-state crystals to reach even longer wavelengths. In addition, there are several promising medical
applications including dental applications such as bone ablation and medical procedures such as opthamology. These
long wavelength sources are also key components in infra-red-counter-measure systems. We have extended our high
performance 1500-nm material to longer wavelengths through optimization of design and epitaxial growth conditions
and report peak CW output powers from single 1-cm diode laser bars of 37W at 1910-nm and 25W at 2070-nm. 1-cm
bars with 20% fill factor were tested under step-stress conditions up to 110-A per bar without failure, confirming
reasonable robustness of this technology. Stacks of such bars deliver high powers in a collimated beam suitable for
pump applications. We demonstrate the natural spectral width of ~ 18nm of these laser bars can be reduced to < 3-nm
with use of an external Volume Bragg Grating, as required for pump applications. We review the developments required
to reach these powers, latest advances and prospects for longer wavelength, higher power and higher efficiency.
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