Page 404 - High Power Laser Handbook

372 So l i d - S t at e La s e r s The National Ignition Facility Laser 373

200 20
180 Request 18
160 10 × Request 16
1st PQ
140 14
10 × 1st PQ 12
Power (mW) 100 2nd PQ 10 Power × 10 (mW)
120
10 × 2nd PQ
8
80
60 6
40 4
Power × 10
20 2
0 0
0 5 10 15 20 25
Time (ns)
Figure 14.10 The temporal pulse shape at the output of the MOR for the two
performance qualification (PQ) shots, designated as 1st PQ (N060329-002-999)
and 2nd PQ (N060329-003-999). The pulse shape was measured with a 1-GHz
transient digitizer.

Lens Diode pump arrays
5-mm rod
Beam- Hollow duct
shaping
module 20X
expander HWP Fiber
POL launch
Rotator Isolator MOR
HWP

POL
QWP
PC1
POL POL
PC2
HWP HWP
(motorized)
Figure 14.11 Schematic of an injection laser system’s (ILS’s) regenerative
amplifier. Light enters the amplifier from the MOR fiber launch at the right of the
figure (dashed blue line). It is collimated, passed through an optical isolator, and
injected through a polarizer (POL) into the main regenerative amplifier cavity (solid
red line). After the beam passes through the Pockels cell (PC1) once, the PC is
switched on, trapping the pulse in the cavity for approximately 30 round-trips. During
each round-trip, the pulse passes twice through a diode-pumped rod amplifier. Before
the final pass, the PC is switched off, and the light exits through a second polarizer
(dashed green line). A motorized half-wave plate (HWP), in combination with a set of
polarizers, controls the energy transmitted to the next stage of amplification. A
second Pockels cell (PC2) can be used to clip off a trailing portion of the pulse that
is meant to saturate the regenerative amplifier for energy stability but is not required
in the rest of the laser. A 20X beam expander, in combination with a beam-shaping
module, sculpts the beam to the desired spatial shape (solid green line).