In nonlinear optics, filament propagation is propagation of a beam of light through a medium without diffraction. This is possible because the Kerr effect causes an index of refraction change in the medium, resulting in self-focusing of the beam. Nonlinear optics is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization P responds nonlinearly to the electric field E of the light. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ... Diffraction is the bending and spreading of waves when they meet an obstruction. ... The Kerr effect or the quadratic electro-optic effect is a change in the refractive index of a material in response to the intensity of an external electric field. ... The refractive index of a material is the factor by which electromagnetic radiation is slowed down (relative to vacuum) when it travels inside the material. ...

Filament propagation of laser pulses in the atmosphere was observed in 1994 by Gérard Mourou and his team at University of Michigan. The balance between the self-focusing refraction and self-attenuating diffraction by ionization and rarefaction of a laser beam of terawatt intensities, created by chirped pulse amplification, in the atmosphere creates "filaments" which act as waveguides for the beam thus preventing divergence. If a light filament drops below the intensity needed for this dynamic balance, called modulation instability, it can merge with another filament and continue propagating without broadening as with all earlier means of sending light. The filaments, having made a plasma, turn the narrowband laser pulse into a broadband pulse having a wholly new set of applications. 1994 (MCMXCIV) was a common year starting on Saturday of the Gregorian calendar, and was designated the International year of the Family. ... Gérard Mourou is a pioneer in the field of electrical engineering and lasers. ... University of Michigan, Ann Arbor The University of Michigan, Ann Arbor (U-M or U of M) is a public coeducational university in Michigan, United States. ... Diffraction is the bending and spreading of waves when they meet an obstruction. ... ... Rarefaction is the reduction of a mediums density, or the opposite of compression. ... Chirped pulse amplification (CPA) is a technique for amplifying an ultrashort laser pulse up to the terawatt level and above with the laser pulse being stretched out temporally prior to amplification. ...

Filament propagation in a semiconductor medium can also be observed in large aperture vertical cavity surface emitting lasers. A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ...