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Routing of anisotropic spatial solitons and modulational instability in liquid crystals


In certain materials, the spontaneous spreading of a laser beam (owing to diffraction) can be compensated for by the interplay of optical intensity and material nonlinearity. The resulting non-diffracting beams are called ‘spatial solitons’ (refs 1–3), and they have been observed in various bulk media4,5,6. In nematic liquid crystals7,8,9, solitons can be produced at milliwatt power levels10,11,12 and have been investigated for both practical applications13 and as a means of exploring fundamental aspects of light interactions with soft matter14,15. Spatial solitons effectively operate as waveguides, and so can be considered as a means of channelling optical information along the self-sustaining filament. But actual steering of these solitons within the medium has proved more problematic, being limited to tilts of just a fraction of a degree16,17,18,19,20. Here we report the results of an experimental and theoretical investigation of voltage-controlled ‘walk-off’ and steering of self-localized light in nematic liquid crystals. We find not only that the propagation direction of individual spatial solitons can be tuned by several degrees, but also that an array of direction-tunable solitons can be generated by modulation instability21,22,23,24,25. Such control capabilities might find application in reconfigurable optical interconnects, optical tweezers and optical surgical techniques.

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Figure 1: Sketch of the sample.
Figure 2: Spatial soliton voltage routing.
Figure 3: Spatial soliton trajectories and walk-off.
Figure 4: Observation of anisotropic modulational instability and generation of multiple spatial solitons for two different biases.


  1. Kivshar, Y. S. & Agrawal, G. P. Optical Solitons (Academic, New York, 2003)

    Google Scholar 

  2. Trillo, S. & Torruellas, W. (eds) Spatial Solitons (Springer, Berlin, 2001)

  3. Boardman, A. D. & Sukhorukov, A. P. (eds) Soliton Driven Photonics (Kluwer Academic, Dordrecht, 2001)

  4. Bjorkholm, J. E. & Ashkin, A. CW self-focusing and self-trapping of light in sodium vapour. Phys. Rev. Lett. 32, 129–132 (1974)

    Article  ADS  Google Scholar 

  5. Duree, G. et al. Observation of self-trapping of an optical beam due to the photorefractive effect. Phys. Rev. Lett. 71, 533–536 (1993)

    Article  ADS  CAS  Google Scholar 

  6. Torruellas, W. E. et al. Observation of two-dimensional spatial solitary waves in a quadratic medium. Phys. Rev. Lett. 74, 5036–5039 (1995)

    Article  ADS  CAS  Google Scholar 

  7. Tabirian, N. V., Sukhov, A. V. & Zel'dovich, B. Y. Orientational optical nonlinearity of liquid crystals. Mol. Cryst. Liq. Cryst. 136, 1–139 (1986)

    Article  Google Scholar 

  8. Khoo, I. C. Liquid Crystals: Physical Properties and Nonlinear Optical Phenomena (Wiley, New York, 1995)

    Google Scholar 

  9. Simoni, F. Nonlinear Optical Properties of Liquid Crystals and Polymer Dispersed Liquid Crystals (World Scientific, Singapore, 1997)

    Book  Google Scholar 

  10. Peccianti, M. et al. Electrically assisted self-confinement and waveguiding in planar nematic liquid crystal cells. Appl. Phys. Lett. 77, 7–9 (2000)

    Article  ADS  CAS  Google Scholar 

  11. Henninot, F., Debailleul, M. & Warenghem, M. Tunable non-locality of thermal non-linearity in dye-doped nematic liquid crystal. Mol. Cryst. Liq. Cryst. 375, 631–640 (2002)

    Article  CAS  Google Scholar 

  12. Assanto, G., Peccianti, M. & Conti, C. Optical spatial solitons in nematic liquid crystals. Opt. Photon. News 14(2), 45–48 (2003)

    Article  ADS  Google Scholar 

  13. Peccianti, M., Conti, C., Assanto, G., De Luca, A. & Umeton, C. All optical switching and logic gating with spatial solitons in liquid crystals. Appl. Phys. Lett. 81, 3335–3337 (2002)

    Article  ADS  CAS  Google Scholar 

  14. Conti, C., Peccianti, M. & Assanto, G. Observation of optical spatial solitons in a highly nonlocal medium. Phys. Rev. Lett. 92, 113902 (2004)

    Article  ADS  Google Scholar 

  15. Conti, C., Peccianti, M. & Assanto, G. Route to nonlocality and observation of accessible solitons. Phys. Rev. Lett. 91, 073901 (2003)

    Article  ADS  Google Scholar 

  16. Torruellas, W. E., Wang, Z., Torner, L. & Stegeman, G. I. Observation of mutual trapping and dragging of two-dimensional spatial solitary waves in a quadratic medium. Opt. Lett. 20, 1949–1951 (1995)

    Article  ADS  CAS  Google Scholar 

  17. Torruellas, W. E., Assanto, G., Lawrence, B. L., Fuerst, R. A. & Stegeman, G. I. All-optical switching by spatial walk-off compensation and solitary-wave locking. Appl. Phys. Lett. 68, 1449–1451 (1996)

    Article  ADS  CAS  Google Scholar 

  18. Crosignani, B. & Salamo, G. Photorefractive solitons. Opt. Photon. News 13(2), 38 (2002)

    Article  ADS  Google Scholar 

  19. Shiek, R., Baek, Y., Stegeman, G. I. & Sohler, W. One-dimensional quadratic walking solitons. Opt. Lett. 24, 83–85 (1999)

    Article  ADS  Google Scholar 

  20. Friedrich, L., Aitchison, J. S., Millar, P. & Stegeman, G. I. Dynamic, electronically controlled, angle steering of spatial solitons in AlGaAs slab waveguides. Opt. Lett. 23, 1438–1440 (1998)

    Article  ADS  CAS  Google Scholar 

  21. Campillo, A. J., Shapiro, S. L. & Suydam, B. R. Periodic breakup of optical beams due to self-focusing. Appl. Phys. Lett. 23, 638–640 (1973)

    ADS  Google Scholar 

  22. Mamaev, A. V., Saffman, M. & Zozulya, A. A. Propagation of dark stripe beams in nonlinear media: snake instability and creation of optical vortices. Phys. Rev. Lett. 76, 2262–2265 (1996)

    Article  ADS  CAS  Google Scholar 

  23. Kip, D., Soljajic, M., Segev, M., Eugenieva, E. & Christodoulides, D. N. Modulational instability and pattern formation in spatially incoherent light beams. Science 290, 495–498 (2000)

    Article  ADS  CAS  Google Scholar 

  24. Shiek, R., Fang, H., Malendevich, R. & Stegeman, G. I. Measurement of modulational instability gain of second-order nonlinear optical eigenmodes in a one-dimensional system. Phys. Rev. Lett. 86, 4528–4531 (2001)

    Article  ADS  Google Scholar 

  25. Peccianti, M., Conti, C. & Assanto, G. Optical modulational instability in a nonlocal medium. Phys. Rev. E 68, 025602(R) (2003)

    Article  ADS  Google Scholar 

  26. Stegeman, G. I. & Segev, M. Optical spatial solitons and their interactions: universality and diversity. Science 286, 1518–1523 (1999)

    Article  CAS  Google Scholar 

  27. Stegeman, G. I., Christodoulides, D. N. & Segev, M. Optical spatial solitons: historical perspectives. IEEE J. Sel. Top. Quant. Electron. 6, 1419–1427 (2000)

    Article  ADS  CAS  Google Scholar 

  28. Nayfeh, A. H. Introduction to Perturbation Techniques (Wiley, New York, 1993)

    MATH  Google Scholar 

  29. Fleischer, J. W., Segev, M., Efremidis, N. K. & Christodoulides, D. N. Observation of two-dimensional discrete solitons in optically induced nonlinear photonic lattices. Nature 422, 147–149 (2003)

    Article  ADS  CAS  Google Scholar 

  30. Weber, M. J. (ed.) CRC Handbook of Laser Science and Technology Suppl. 2, Optical Materials (CRC, New York, 1995)

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We thank A. Alberucci, G. Coschignano and A. Fratalocchi for support in the laboratory.

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Correspondence to Gaetano Assanto.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Video 1

This movie shows the voltage-controlled steering of a spatial soliton acquired by the CCD camera. (MPG 2383 kb)

Supplementary material Word file

The file contains 4 supplementary figures, and equations. Supplementary figures 1-3 report additional experimental results. Supplementary figure 4 shows the coefficients of the theoretical model. Supplementary equations concern a brief outline of the derivation of the model and the determination of the director angle profile. (DOC 434 kb)

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Peccianti, M., Conti, C., Assanto, G. et al. Routing of anisotropic spatial solitons and modulational instability in liquid crystals. Nature 432, 733–737 (2004).

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