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Highly efficient diode end pumped Nd:YAG slab laser

: Giesekus, J.; Schmidt, G.; Schnitzler, C.; Mans, T.; Wester, R.; Du, K.; Loosen, P.; Poprawe, R.

Scheps, R. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Solid state lasers IX. Proceedings : 25 - 26 January 2000, San Jose, California
Bellingham/Wash.: SPIE, 2000 (SPIE Proceedings Series 3929)
ISBN: 0-8194-3546-5
Solid State Lasers Conference <9, 2000, San Jose/Calif.>
Fraunhofer ILT ()
solid-state laser; diode pumped laser; high power laser; slab laser; Nd-YAG-laser; unstable resonator; ray tracing; ANSYS

High power diode pumped solid state lasers are auspicious sources for various applications in material processing. The solid state laser we report on is a Nd:YAG slab laser, that is partially end pumped from two ends by the line focus of two diode laser stacks. The pumped volume has a rectangular cross section. The resonator is configured, so that it is stable in the plane of small dimension and off axis unstable in the plane of large dimension of the gain cross section. Unlike conventional slab laser design, in which the laser beam takes zick zack path inside the slab crystal, in the present design the beam goes straight through the crystal with perpendicular end faces. The pump radiation of the stacked diode laser bars is homogenised by using a planar waveguide. For designing the integrating waveguide a ray-tracing model was developed to calculate the distribution of the absorbed pump power. In order to get a thermal lens, which behaves like a cylindrical lens, it is important to get a smooth pump line, that underfills the slab and forms a gain sheet in the central portion of the stab. To examine the influence of the pump light distribution a FEM model was set up to calculate the thermal and mechanical load of the crystal. Using two stacks with 14 diodes each, a cw output power of 350 W has been demonstrated.