Page 242 - High Power Laser Handbook

210 So l i d - S t at e La s e r s Nd:YAG Ceramic ThinZag® High-Power Laser Development 211

9.1.2 TZ-2 Module Development
The next scaling path to higher average power was to incorporate a
second gain slab into the basic ThinZag laser design. The volume was
increased by increasing the slab length by a factor of 1.5, as well as by
doubling the number of slabs from one slab to two, for a factor of
3 total increase in excited volume. The pump power was also increased
by a factor of 1.5 for an overall deposited pump power increase of 4.5
(1.5 × 2 × 1.5), thereby projecting an increase in output power to over
5 kW (1.2 kW × 4.5 = 5.4 kW).
The two-slab ThinZag laser (designated TZ-2) was also pumped
from both sides by Nuvonyx diode pump sources, each consisting of
80-W diode bars in series oriented with the fast axis in the horizontal
plane. To ensure uniform pumping, the pump light was optically
mixed in an optical “scrambler” before reaching the laser module.
These scramblers were made of single blocks of fused silica, which
acted as a light guide by confining the 808-nm pump radiation using
total internal reflection (TIR). Measurements of the pump deposition
profile were made using a single scrambler with one of the ThinZag
windows. CCD images were taken of the pump light after it passed
through the optical scrambler–window combination and impinged
onto a Lambertian scattering surface. The measured profiles showed
excellent deposition uniformity.
In the center of Fig. 9.5, which shows the TZ-2, the two-slab Thin-
Zag laser head is positioned to show some of the gold-coated metal

Figure 9.5 TZ-2 laser, showing diode pump source and optical scramblers
pumping device from two sides.