Page 240 - High Power Laser Handbook

208 So l i d - S t at e La s e r s Nd:YAG Ceramic ThinZag® High-Power Laser Development 209

over the years at Textron Defense Systems’ laser laboratories using
the ThinZag configuration. These tests have included flash lamp-
4,5
and laser-pumped laser arrangements using liquid dye, dye-
6
impregnated plastics, and Yb/Er:Glass, Nd:YLF, and Cr:LiSAF
crystals. 7–9
This section describes the progression of ThinZag laser designs
from a 1-kW single-slab device (TZ-1) to a 5-kW two-slab device
(TZ-2) to a larger-area two-slab nominal 15-kW device (TZ-3). The
TZ-3 laser module is the basic building block for achieving higher-
power (100-kW) output. Initial tests consist of coupling three TZ-3
modules as a single-aperture power oscillator. The Joint High Power
Solid-State Laser (JHPSSL) 100-kW laser consists of six similar mod-
ules operating as a single-aperture power oscillator.

9.1.1 TZ-1 Module Development
The first diode-pumped Nd:YAG ThinZag laser (designated TZ-1) was
a single-slab design with nominal output ~1 kW. ThinZag lasers at that
time used short-pulse lasers or short-pulse flash lamp pumping (~1 µs)
as an excitation source. The highest power achieved was about 80 W
from a Cr:LiSAF laser, which operated at up to 10 Hz with output up to
8 J/pulse. 4,10,11 The thermal loads for the diode-pumped high-power
devices are larger by more than 2 orders of magnitude and call for
much greater attention to thermal control of the laser components.
The TZ-1 consisted of a single slab of Nd:YAG (either ceramic or
crystal) that is pumped from both sides by high-power 808-nm con-
tinuous wave (CW) laser diode arrays. The TZ-1 laser achieved high-
power output for extended runs, as shown in Fig. 9.2.
In comparing crystalline and ceramic Nd:YAG samples, it was
found that the ceramic samples were generally optically superior to
the crystalline samples. Nd:YAG ceramic also displayed better [Nd]
uniformity compared to crystal. Typical measurements using a

1400
1200
1000
Power (W) 800
600
400
200
0
0 20 40 60
Time (s)
Figure 9.2 Demonstrated steady-state performance of TZ-1 laser using
ceramic slab.