Pumping fiber lasers is the driving force for the development of high brightness, mid power, passively cooled, fiber
coupled diode lasers. We compare concepts for providing 50 W in a 100 micron fiber at the optimum fiber laser pump
wavelength of 976 nm. The set up is experimentally demonstrated and compared to the optical analysis.
Three basic diode laser concepts are included into this comparison: single emitters, high density emitter arrays and low
density emitter arrays on bars.
Low density stacking in the horizontal direction with increasing the filling factor by a microlens array is the first concept.
For this concept two diode bars with low filling factor are fast and slow axis collimated. Beam transformation, shaping
and focusing are similar to the second concept.
In the second concept a diode laser array with high filling factor is regarded. An 800 μm diode laser bar consists of an
array of four or five emitters. Two bars are polarization coupled and collimated with single lenses. Beam symmetrization
is performed by the well known step mirror. A simple anamorphotic optic enables beam shaping and fiber coupling.
The third one, single emitters, represents optical beam combining of laser diodes that are high density stacked in the
vertical direction. Five emitters are placed in an optical stack, each one collimated with its own lens. Two optical stacks
are polarization coupled and focused on the fiber end. The three concepts are compared in terms of power efficiency and
complexity, and the results of prototype systems are presented.