
480
Laser-Induced Damage in Optical Materials
e results can be described by Lambert–Beer’s law for optically thin samples. Taking
into account surface, single- and two-photon absorption, the total absorption A reads as
A
dI
I
AIdA
H
d
Surface
==+⋅⋅= ++
⎛
⎜
⎞
⎟
⋅
0
β
τ
(17.2)
where
A
0
describes the linear absorbance, which is given by the sum of bulk absorbance α ⋅ d
and (linear) surface absorbance A
Surface
β is the second-order nonlinear absorption coecient (I, incident intensity; d, sample
thickness; α, linear absorption coecient; H, uence; τ, pulse length)
us, from the linear slope of absorbance over intensity in Figure 17.4, the nonlinear
absorptio