Self-focusing is a non-linear optical process induced by the change in refractive index of materials exposed to intense electromagnetic radiation.[1][2] A medium whose refractive index increases with the electric field intensity acts as a focusing lens for an electromagnetic wave characterized by an initial transverse intensity gradient, as in a laser beam.[3] The peak intensity of the self-focused region keeps increasing as the wave travels through the medium, until defocusing effects or medium damage interrupt this process. Self-focusing of light was discovered by Gurgen Askaryan.
Self-focusing is often observed when radiation generated by femtosecond lasers propagates through many solids, liquids and gases. Depending on the type of material and on the intensity of the radiation, several mechanisms produce variations in the refractive index which result in self-focusing: the main cases are Kerr-induced self-focusing and plasma self-focusing.
- ^ Cumberbatch, E. (1970). "Self-focusing in Non-linear Optics". IMA Journal of Applied Mathematics. 6 (3): 250–62. doi:10.1093/imamat/6.3.250.
- ^ Mourou, Gerard A.; Tajima, Toshiki; Bulanov, Sergei V. (2006). "Optics in the relativistic regime". Reviews of Modern Physics. 78 (2): 309. Bibcode:2006RvMP...78..309M. doi:10.1103/RevModPhys.78.309.
- ^ Rashidian Vaziri, M.R. (2015). "Comment on 'Nonlinear refraction measurements of materials using the moiré deflectometry'". Optics Communications. 357: 200–1. Bibcode:2015OptCo.357..200R. doi:10.1016/j.optcom.2014.09.017.