Abstract

We report on experiments dealing with the propagation of a collimated laser beam in a dye doped nematic confined in a capillary of optical fiber size. The nematic is aligned in a such a way that the source beam is self focused. The behavior of the beam - focusing, multifocus regime, filamentation and undulation - already observed in larger cylindrical geometry and pure nematic is shown here to be reproduced in the dye doped medium, at much lower powers. Another feature is reported here: a stable regime looking like a waveguide appears in certain conditions, in which the beam to propagate in a narrow tube. This regime is simply modeled in terms of saturated reorientation of the nematic.

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References

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  1. N. V. Tabiryan, A. V. Sukhov and B. Ya Zeldovich, "The Orientational Optical Nonlinearity of Liquid Crystals," Mol. Cryst. Liq. Cryst. 136, 1, (1986)
    [CrossRef]
  2. I. C. Khoo, "Nonlinear Optics of Liquid Crystals" in Prog. Opt., 27, 105, (1988)
    [CrossRef]
  3. E. Santamato, "Nonlinear optical materials and devices for applications in information technology," A. Miller ed., (Kluwer Academic, Dordrecht, Netherlands, 1995)
  4. E. Santamato and Y. R. Shen, in A guide to Liquid Crystal research, P.J. Collings and J. Patel ed. (Oxford University Press, New York, 1997)
  5. L. Marrucci and Y. R. Shen, in The optics of thermotropic liquid crystals, R. Sambles and S. Elston ed. (Taylor and Francis , London, 1997)
  6. I. C. Khoo and S. T. Wu, in Optics and non linear optics of Liquid Crystals, Vol 1,(World Scientific, Singapore, 1993) Chap. 3, 4.
    [CrossRef]
  7. I. C. Khoo and F. Simoni, in The Physics of Liquid Crystalline materials, (Gordon and Breach, London, 1991) Chap 14.
  8. F. Simoni, in Nonlinear optical properties of Liquid Crystals and PDLC, Series on Liquid Crystals, Vol 2, (World Scientific, Singapore, 1997)
    [CrossRef]
  9. E. Braun, L. Faucheux, A. Libchaber, "Strong self focusing in nematic liquid crystals," Phys. Rev. A, 48-1, 611, (1993)
    [CrossRef]
  10. E. Braun, L. Faucheux, A. Libchaber, D. W. McLaughlin, D. J. Muraki and M. J. Shelley, "Filamentation and undulation of self focused laser beams in liquid crystals," Europhys. Lett., 23 (4), 239, (1993)
    [CrossRef]
  11. D. W. McLaughlin, D. J. Muraki and M. J. Shelley, "Light interacting with liquid crystals," Physica D, 68, 116, (1993).
    [CrossRef]
  12. D. W. McLaughlin, D. J. Muraki, M. J. Shelley and X. Wang, "A paraxial model for optical self focussing in a nematic liquid crystal," Physica D, 88, 55, (1995)
    [CrossRef]
  13. D. W. McLaughlin, D. J. Muraki and M. J. Shelley, "Self focused optical structures in a nematic liquid crystal," Physica D, 97, 471, (1996)
    [CrossRef]
  14. O. Duhem, J. F. Henninot, G. Abbate and M. Warenghem, "Observation of liquid crystal alignment in capillaries using a new experimental approach," Mol. Cryst. Liq. Cryst., in press
  15. J. F. Henninot, M. Warenghem and N. Tabiryan, "Leakography: visualization of losses in fibers and fiber optics systems using liquid crystals," Mol. Cryst. Liq. Cryst., in press
  16. M. Warenghem, D. Louvergneaux and F. Simoni, "Experimental results on the director distribution in hybrid nematic films using ATIR," Mol. Cryst. Liq. Cryst., 282, 235, (1996)
    [CrossRef]
  17. I. Janossy, A. D. Lloyd and B. S. Wherrett, "Anomalous Optical Freedericksz Transition in an Absorbing Liquid Crystal," Mol. Cryst. Liq. Cryst., 179, 1, (1990)
  18. D. Paparo, P. Maddalena, G. Abbate, E. Santamato and I. Janossy, "Wavelength dependence of optical reorientation in dye doped nematics," Mol. Cryst. Liq. Cryst., 251, 73, (1994)
    [CrossRef]

Other (18)

N. V. Tabiryan, A. V. Sukhov and B. Ya Zeldovich, "The Orientational Optical Nonlinearity of Liquid Crystals," Mol. Cryst. Liq. Cryst. 136, 1, (1986)
[CrossRef]

I. C. Khoo, "Nonlinear Optics of Liquid Crystals" in Prog. Opt., 27, 105, (1988)
[CrossRef]

E. Santamato, "Nonlinear optical materials and devices for applications in information technology," A. Miller ed., (Kluwer Academic, Dordrecht, Netherlands, 1995)

E. Santamato and Y. R. Shen, in A guide to Liquid Crystal research, P.J. Collings and J. Patel ed. (Oxford University Press, New York, 1997)

L. Marrucci and Y. R. Shen, in The optics of thermotropic liquid crystals, R. Sambles and S. Elston ed. (Taylor and Francis , London, 1997)

I. C. Khoo and S. T. Wu, in Optics and non linear optics of Liquid Crystals, Vol 1,(World Scientific, Singapore, 1993) Chap. 3, 4.
[CrossRef]

I. C. Khoo and F. Simoni, in The Physics of Liquid Crystalline materials, (Gordon and Breach, London, 1991) Chap 14.

F. Simoni, in Nonlinear optical properties of Liquid Crystals and PDLC, Series on Liquid Crystals, Vol 2, (World Scientific, Singapore, 1997)
[CrossRef]

E. Braun, L. Faucheux, A. Libchaber, "Strong self focusing in nematic liquid crystals," Phys. Rev. A, 48-1, 611, (1993)
[CrossRef]

E. Braun, L. Faucheux, A. Libchaber, D. W. McLaughlin, D. J. Muraki and M. J. Shelley, "Filamentation and undulation of self focused laser beams in liquid crystals," Europhys. Lett., 23 (4), 239, (1993)
[CrossRef]

D. W. McLaughlin, D. J. Muraki and M. J. Shelley, "Light interacting with liquid crystals," Physica D, 68, 116, (1993).
[CrossRef]

D. W. McLaughlin, D. J. Muraki, M. J. Shelley and X. Wang, "A paraxial model for optical self focussing in a nematic liquid crystal," Physica D, 88, 55, (1995)
[CrossRef]

D. W. McLaughlin, D. J. Muraki and M. J. Shelley, "Self focused optical structures in a nematic liquid crystal," Physica D, 97, 471, (1996)
[CrossRef]

O. Duhem, J. F. Henninot, G. Abbate and M. Warenghem, "Observation of liquid crystal alignment in capillaries using a new experimental approach," Mol. Cryst. Liq. Cryst., in press

J. F. Henninot, M. Warenghem and N. Tabiryan, "Leakography: visualization of losses in fibers and fiber optics systems using liquid crystals," Mol. Cryst. Liq. Cryst., in press

M. Warenghem, D. Louvergneaux and F. Simoni, "Experimental results on the director distribution in hybrid nematic films using ATIR," Mol. Cryst. Liq. Cryst., 282, 235, (1996)
[CrossRef]

I. Janossy, A. D. Lloyd and B. S. Wherrett, "Anomalous Optical Freedericksz Transition in an Absorbing Liquid Crystal," Mol. Cryst. Liq. Cryst., 179, 1, (1990)

D. Paparo, P. Maddalena, G. Abbate, E. Santamato and I. Janossy, "Wavelength dependence of optical reorientation in dye doped nematics," Mol. Cryst. Liq. Cryst., 251, 73, (1994)
[CrossRef]

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Figures (6)

Fig. 1.
Fig. 1.

Setup; 1.a: side view ; 1.b: section view.

Fig. 2
Fig. 2

Video recording showing the behavior of the source beam as the input power is increased then decreased. [Media 1]

Fig. 3.
Fig. 3.

Schematic representation of the observed “self waveguiding” structure, as shown on the upper photograph on the right.

Fig. 4.
Fig. 4.

Photographs extracted from the movie: Up (= Fig. 2): the “self waveguiding structure”; Down: the isotropic zone has been underlined together with the fiber; (part of the movie not presented here).

Fig.5.
Fig.5.

Schematic representation of the ≪ tube ≫. This is a picture valid only in the plane of the input beam polarization, namely oxz (Fig. 1). Up: radial director distribution. Down: associated extraordinary index profiles for different sections.

Fig. 6
Fig. 6

Calculated index profiles, including T(r), with T(r) = 33°C (no gradient) and a linear gradient with T(0) = 33°C; T(120) = 25°C; a maximum occurs around 12 μm

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