non-linear optical effect

https://doi.org/10.1351/goldbook.N04197
An effect brought about by electromagnetic radiation the magnitude of which is not proportional to the irradiance. Non-linear optical effects of importance to @P04588@ are @H02744@, lasers, Raman shifting, @U06574@, and others.
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2256 [Terms] [Paper]