
NONLINEAR OPTICS 449
Laser
Pump1
Pump2
Nonlinear
crystal
Conjugate
Sample
Object
(A)
Laser
Ref
Detector
Nonlinear
crystal
Sample
Object
(B)
Figure 14.7 Applications of third-order processes. A nonlinear crystal can be used to
conjugate a wave, or to amplify it. (A) Phase conjugation. (B) Wave amplification.
0
χ
[3]
E
object
+E
∗
object
E
pump1
+E
pump1
E
pump2
+E
pump2
(14.34)
D
conj
=
0
χ
[3]
E
∗
object
E
pump1
E
pump2
. (14.35)
If the second pump has the same wavefront shape as the rst, but is traveling in the opposite
direction
E
pump2
= CE
∗
pump1
, (14.36)
where C is a constant, then
D
conj
=
0
χ
[3]
E
∗
object
C
E
pump1
2
. (14.37)
This source will result in a propagating wave conjugate to E