
638 Kerr Lensing in a Cavity
r
0
r
-f
n l
L
r
a
L
n l
Figure E.1 A simplified power limiter, including a nonlinear lens acting on a collimated beam of
radius r
0
, and an aperture of radius r
a
. At high power, the nonlinear lens acquires a focal length of
f
nl
. The example shown refers to a negative nonlinearity leading to defocusing.
where T
0
=(r
a
/r
0
)
2
is the transmission without the nonlinear lens, r =r
0
−Lr
0
/f
nl
,
and C is a positive constant (for defocusing). Clearly the transmission is maxi-
mum for low intensities and negligible self-lensing. If I
0
(t) represents a pulse
envelope the transmission decreases in the center, which may lead to pulse
broadening and limits ...