
142
Laser-Induced Damage in Optical Materials
To understand how damage can occur in S-on-1 experiments, let us consider a sam-
ple that is illuminated by a train of equally spaced (period T) identical pulses of uence
F < F
1
and duration τ
p
. e rst pulse of the train produces a CB electron density accord-
ing to Equation 5.6 of
N
a
F
eNeQNe
m
p
m
aF aF aF
1
0
1
00 0
1=
⎛
⎜
⎞
⎟
−
()
+=+
−
β
τ
,
(5.12)
where Q is the electron density produced by MPA and impact ionization. Assuming
a lifetime of these electrons of T
cv
(of the various processes in Figure 5.6 only band-
to-band relaxation is considered), the population decays to
NNe
TT
cv
− /
before the
second pulse a ...