optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

, a nematicon is a

spatial soliton Spatial may refer to: *Dimension *Space *Three-dimensional space In geometry, a three-dimensional space (3D space, 3-space or, rarely, tri-dimensional space) is a mathematical space in which three values ('' coordinates'') are required to d ...

in nematic

liquid crystals Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as i ...

(NLC). The name was invented in 2003 by G. Assanto. and used thereafter Nematicons are generated by a special type of optical nonlinearity present in NLC: the light induced reorientation of the molecular director (''i.e.'' the average molecular orientation). This nonlinearity arises from the fact that the molecular director (i.e., the optic axis of the corresponding uniaxial) tends to align along the electric field of light. Nematicons are easy to generate (with mW

optical power In optics, optical power (also referred to as dioptric power, refractive power, focal power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the ...

or less ) because the NLC dielectric medium exhibits the following properties: * A very large nonlinear response : the effective nonlinearity is typically eight orders of magnitude larger than that of

carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is an inorganic compound with the chemical formula and structure . It is also considered as the anhydride of thiocarbonic acid. It is a colorless, flammable, neurotoxic liquid that is used as ...

. This means that much lower optical powers are necessary to obtain the same

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

variation (increase) or self-focusing to balance out diffraction. * A nonlocal response : the nonlinear response is not limited to the location of the optical field. Instead the response profile is wider than the light beam. A high nonlocality allows for stable soliton propagation even in the case of two transverse dimensions. Higher or lower powers than the exact value required for a soliton to exist lead to breathing solitons. * A saturable all-optical response: the director of the liquid crystal tends to align along the electric field of the light beam. For powerful beams the molecular director becomes parallel to the field and no further reorientation is possible. Response saturation also stabilizes two-dimensional solitons. Since the reorientational optical nonlinearity of nematic liquid crystals is accompanied by an electro-optic response to low-frequency electric fields, i.e. applied voltages, nematicons and the associated waveguides can be steered in angle and routed in space by the application of an external bias, leading to reconfigurable interconnects. In waveguide arrays where discrete solitons are knows to form, discrete nematicons have also been demonstrated
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References

External links

Spatial optical solitons in liquid crystals
{{Webarchive, url=https://web.archive.org/web/20070814124420/http://www.elis.ugent.be/ELISgroups/lcd/research/soliton.php , date=2007-08-14 , a short introduction (Ghent University). Solitons Nonlinear optics Liquid crystals

See also

References

External links