DFWM and optical phase conjugation

4 Degenerate four-wave mixing (DFWM) and optical phase conjugation 

The pump beams 1 and 3 are counterpropagating. The signal beam 4 is emitted in the direction opposite to the probe beam 2. Its intensity depends on and on the intensities of beams 1, 2, and 3 according to Eq. (3-31) [27]. 

At a conventional mirror, only the wave vector component normal to the surface changes sign, while the tangential components remain unchanged. The propagation direction of the reflected ray depends on the angle between the surface normal 

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Tlie usual experimental techniques developed to study the optical Kerr effect in materials have already been described in a preceding chapter of this book. We only mention here the methods which have especially been used for nanocomposite materials as colloidal solutions or thin films Degenerate four-wave mixing (DFWM) and optical phase conjugation, which provide the modulus of x only and may be completed by Interferometry techniques to get its phase as well, optical limiting, optical Kerr shutter, and z-scan, which is probably the most common technique used in recent years due to its ability to provide simultaneously the nonlinear refraction and absorption coefficients of the same sample point [118],... 

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