Collective name applied to techniques related to non-linear optical effects.
Notes:
- Some of these spectroscopies are four-wave mixing,
hole burning, photon echoes, time-resolved coherent anti-Stokes Raman (CARS),
transient grating and stimulated pumping. These techniques differ in the nature of
the
pulse sequence, the geometry and the choice of a spatial direction (phase matching),
as well as the mode of detection.
- Low order non-linear techniques, such as three-wave mixing, are related to the
second order polarization. For a random isotropic medium with inversion symmetry,
the second-order polarization vanishes and then the lowest order optical non-linear
techniques, as well as the higher order non-linear techniques are related to the
third-order polarization and the corresponding 'hyper-susceptibility'.
Source:
PAC, 2007, 79, 293
(Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006))
on page 374