Comparison between rod and slab architectures for high power diode side-pumped Q-switched Nd:YAG lasers

A comparison between two side-pumping configurations of Nd:YAG Q-switched lasers is presented, based on experimental results and theoretical models developed by us. The first architecture, experimentally and theoretically tested, used a close-coupled pumping design where bare diode lasers were placed nest to a Brewster cut rod. This laser produced 10 W average power at 10 kHz repetition rate with 30 ns pulse width and good beam quality, 12% light to light conversion efficiency was achieved with the added advantage of simplicity. The second arrangement, theoretically tested, was a zig-zag slab layout where the diode light was collimated with micro-lenses prior to being absorbed in a strip like area inside the slab. This design eliminated the problem of thermal induced birefringence, through the Cartesian symmetry of the thermal gradients developed inside the slab, while averaging out pump nonuniformities through the zig-zag path, thus yielding high beam fill factor within the pump volume.