Abstract

We report the results of an investigation carried on Methyl Red-doped nematic liquid crystals with the aim of studying the basic mechanism of the extraordinarily large nonlinear response recently reported. We show that the experimental data can be explained as due to light-induced modifications of the anchoring conditions leading to director reorientation on the irradiated surface, which in turn gives rise to a bulk reorientation through the cell. We have called this phenomenon SINE (Surface Induced Nonlinear Effect) to remind that it occurs “without” (=sine in latin language) a direct optical or electric torque on the director in the bulk.

© Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. F. Simoni, Nonlinear Optical Properties of Liquid Crystals and Polymer Dispersed Liquid Crystals, (World Scientific, Singapore 1997).
    [CrossRef]
  2. B.Ya. Zel'dovich, N.F. Pilipetskii, A.V. Sukhov and N.V. Tabiryan, "Giant Optical Nonlinearity of a nematic liquid crystal," JETP Lett. 31, 264 (1980).
  3. I. Janossy, A.L. Lloyd and B.S. Wherret, "Anomalous optical Freedericksz transition in absorbing liquid crystal," Mol. Cryst. Liq. Cryst. 179,1(1990).
  4. I.C. Khoo, S. Slussarenko, B.D. Guenther, M-Y. Shih, P.H. Chen and W.V. Wood, "Optically induced space-charge fields, dc voltage and extraordinarily large nonlinearity in dye-doped liquid crystals," Opt. Lett. 23,253(1998).
    [CrossRef]
  5. R. Macdonald, P. Meindl, G. Chilaya, D. Sikharulidze, "Photoexitation of space charge fields and reorientation of a nematic liquid crystal of discotic molecules," Opt. Comm 150, 195 (1998).
    [CrossRef]
  6. K. Ichimura, Y. Hayashi, T. Ikeda, H. Aikiyama, N. Ishizuki, "Photo-optical liquid crystal cells driver by molecular rotors," Appl. Phys. Lett. 63, 449 (1993).
    [CrossRef]
  7. W.M. Gibbons, P.J. Shannon, S.T. Sun, B.J. Swetlin, "Surface-mediated alignment of nematic liquid crystals with polarized laser light," Nature 351, 49 (1991).
    [CrossRef]
  8. M. Born and E. Wolf, Principles of Optics - Sixth Ed., (Pergamon Press, Oxford 1980).
  9. C. Umeton, A. Sgr� and F.Simoni, "Optically induced phase shift in nematic liquid crystals with hybrid alignment," J. Opt. Soc. Am. B 4, 1938 (1987).
    [CrossRef]
  10. O. Francescangeli, F. Simoni, S. Slussarenko, D. Andrienko, V. Reshetnyak and Y.Reznikov, "Light-induced surface sliding of the nematic director in liquid crystals," Phys. Rev. Lett. 82, 1855 (1999).
    [CrossRef]
  11. I. Janossy and L Szabados, "Optical reorientation of nematic liquid crystals in the presence of photoisomerisation," Phys. Rev. E 58, 4598 (1998).
    [CrossRef]
  12. I.C. Khoo, R.G. Lindquist, R.R. Michael, R.J. Mansfield and P. LoPresti, "Dynamics of picosecond laser-induced density, temperature and flow-reorientation effects in the mesophases of liquid crystals," J. Appl. Phys. 69, 3853 (1991).
    [CrossRef]

Other (12)

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

B.Ya. Zel'dovich, N.F. Pilipetskii, A.V. Sukhov and N.V. Tabiryan, "Giant Optical Nonlinearity of a nematic liquid crystal," JETP Lett. 31, 264 (1980).

I. Janossy, A.L. Lloyd and B.S. Wherret, "Anomalous optical Freedericksz transition in absorbing liquid crystal," Mol. Cryst. Liq. Cryst. 179,1(1990).

I.C. Khoo, S. Slussarenko, B.D. Guenther, M-Y. Shih, P.H. Chen and W.V. Wood, "Optically induced space-charge fields, dc voltage and extraordinarily large nonlinearity in dye-doped liquid crystals," Opt. Lett. 23,253(1998).
[CrossRef]

R. Macdonald, P. Meindl, G. Chilaya, D. Sikharulidze, "Photoexitation of space charge fields and reorientation of a nematic liquid crystal of discotic molecules," Opt. Comm 150, 195 (1998).
[CrossRef]

K. Ichimura, Y. Hayashi, T. Ikeda, H. Aikiyama, N. Ishizuki, "Photo-optical liquid crystal cells driver by molecular rotors," Appl. Phys. Lett. 63, 449 (1993).
[CrossRef]

W.M. Gibbons, P.J. Shannon, S.T. Sun, B.J. Swetlin, "Surface-mediated alignment of nematic liquid crystals with polarized laser light," Nature 351, 49 (1991).
[CrossRef]

M. Born and E. Wolf, Principles of Optics - Sixth Ed., (Pergamon Press, Oxford 1980).

C. Umeton, A. Sgr� and F.Simoni, "Optically induced phase shift in nematic liquid crystals with hybrid alignment," J. Opt. Soc. Am. B 4, 1938 (1987).
[CrossRef]

O. Francescangeli, F. Simoni, S. Slussarenko, D. Andrienko, V. Reshetnyak and Y.Reznikov, "Light-induced surface sliding of the nematic director in liquid crystals," Phys. Rev. Lett. 82, 1855 (1999).
[CrossRef]

I. Janossy and L Szabados, "Optical reorientation of nematic liquid crystals in the presence of photoisomerisation," Phys. Rev. E 58, 4598 (1998).
[CrossRef]

I.C. Khoo, R.G. Lindquist, R.R. Michael, R.J. Mansfield and P. LoPresti, "Dynamics of picosecond laser-induced density, temperature and flow-reorientation effects in the mesophases of liquid crystals," J. Appl. Phys. 69, 3853 (1991).
[CrossRef]

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (3)

Fig.1.
Fig.1.

Signal vs time in case of cw excitation. The incident pump intensity is 56 mW/cm2 and the cell thickness is 23 µm. Signal oscillations are visible both during rising and relaxation (see text). Inset: Signal rise under cw irradiation at lower intensity (I=5.6 mW/cm2). The initial slope can be fitted by assuming S∝Eγ with γ=4.8, as shown by the dashed line.

Fig.2.
Fig.2.

Signal vs time in case of pulsed excitation. The impinging energy density is E=10 mJ/cm2 in curves a and c and E=6 mJ/cm2 in curve b. In case of curve c a dc voltage V=12 V is applied across the cell thus creating a field perpendicular to the glass plates. Cell thickness=23 µm. All the curves decay to zero for a longer time.

Fig.3.
Fig.3.

Phase shift δ vs d. The experimental data (symbols) are satisfactory fitted by assuming a linear dependence of δ on the thickness d (full line). The value δ=3π corresponding to d=23 µm may be overestimated.

Equations (5)

Equations on this page are rendered with MathJax. Learn more.

S C · e α d sin 2 ( 2 ϕ ) sin 2 ( δ 2 )
d θ d z = c
L 1 c = 1 2 sin ( 2 θ 1 2 θ 1 * )
θ 1 = H E 1 + L 1 d H E and θ = H E ( z d 1 )
δ n = 1 6 ε ε Δ ε ( H E ) 2

Metrics