Nematicon

In optics, a nematicon is a spatial optical soliton in a nematic liquid crystal. The name was invented in 2003 by G. Assanto ^[1]. Nematicons are generated by the special type of optical nonlinearity that is present in nematic LCs: the optical field induced director reorientation. This nonlinearity arises from the fact that the liquid crystal director (i.e. the average molecular orientation) tends to align along the optical electric field. Nematicons are very easy to generate (with a few mW of optical power^[2]) because the nonlinearity has the following properties:

• A very large nonlinear coefficient : the nonlinearity is typically eight orders of magnitude larger than that of carbon disulfide. This means that much lower optical power is necessary for obtaining the same refractive index variation.
• The nonlocal response : nonlocality means that the nonlinear response is not limited to the exact location of the optical field. Instead the nonlinear response is spread out. A high nonlocality leads to a stable soliton propagation. A higher and lower power than the ideal soliton power will lead to breathing solitons^[3].

The difference between a nonlocal and a local response. For a local response a intensity profile gives rise to a dirac response in refractive index. For a nonlocal response the refractive index change is blurred.

• The saturability: the director of the liquid crystal tends to align along the optical electric field. For very strong optical fields the director is aligned along the optical field and no further reorientation is possible.

See also

• Soliton (optics)
• Liquid crystal

References

1. ^ G. Assanto, M. Peccianti, C. Conti (2003). "Nematicons: Optical Spatial Solitons in Nematic Liquid Crystals". Opt. Photon. News 14: 44–48. Bibcode 2003OptPN..14...44A. doi:10.1364/OPN.14.2.000044.  [1]
2. ^ J. Beeckman, K. Neyts, X. Hutsebaut, C. Cambournac, M. Haelterman (2004). "Simulations and Experiments on Self-focusing Conditions in Nematic Liquid-crystal Planar Cells". Opt. Express 12: 1011–1018. Bibcode 2004OExpr..12.1011B. doi:10.1364/OPEX.12.001011. PMID 19474916.  [2][3]
3. ^ A. Snyder, D. Mitchell (1997). "Accessible Solitons". Science 276 (5318): 1538–1541. doi:10.1126/science.276.5318.1538.  [4]

External links

• Spatial optical solitons in liquid crystals, a short introduction (Ghent University).