Abstract

Light-induced molecule reorientation in dye-doped liquid crystals has been applied to nonlinear spatial filtering of periodic patterns. Photoisomerization of azo-dye molecules leads to local alignment changes in the liquid-crystal molecules because of interaction among the molecules. Consequently the polarization of transmitted light is modulated, depending on the induced light intensity. By selection of suitable polarization of the transmitted light self-aligned filtering is realized. Both temporal response and filtering efficiencies have been experimentally investigated.

© 1996 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  7. T. Ikeda, T. Sasaki, K. IchimuraNature (London) 361, 428 (1993).
    [CrossRef]

1994 (2)

I. C. Khoo, H. Li, Y. LiangOpt. Lett 19, 1723 (1994).
[CrossRef] [PubMed]

C. Ulrich, L. HesselinkAppl. Opt. 33, 744 (1994).
[CrossRef]

1993 (1)

T. Ikeda, T. Sasaki, K. IchimuraNature (London) 361, 428 (1993).
[CrossRef]

1992 (1)

1991 (1)

W. M. Gibbons, P. J. Shannon, S.-T. Sun, B. J. SwetlinNature (London) 351, 49 (1991).
[CrossRef]

1990 (1)

1970 (1)

For example, R. GreefRev. Sci. Instrum. 41, 532 (1970).
[CrossRef]

Brady, D. J.

Chen, A. G.

Gibbons, W. M.

W. M. Gibbons, P. J. Shannon, S.-T. Sun, B. J. SwetlinNature (London) 351, 49 (1991).
[CrossRef]

Greef, R.

For example, R. GreefRev. Sci. Instrum. 41, 532 (1970).
[CrossRef]

Hesselink, L.

Ichimura, K.

T. Ikeda, T. Sasaki, K. IchimuraNature (London) 361, 428 (1993).
[CrossRef]

Ikeda, T.

T. Ikeda, T. Sasaki, K. IchimuraNature (London) 361, 428 (1993).
[CrossRef]

Khoo, I. C.

I. C. Khoo, H. Li, Y. LiangOpt. Lett 19, 1723 (1994).
[CrossRef] [PubMed]

Li, H.

I. C. Khoo, H. Li, Y. LiangOpt. Lett 19, 1723 (1994).
[CrossRef] [PubMed]

Liang, Y.

I. C. Khoo, H. Li, Y. LiangOpt. Lett 19, 1723 (1994).
[CrossRef] [PubMed]

Mobus, G.

Sasaki, T.

T. Ikeda, T. Sasaki, K. IchimuraNature (London) 361, 428 (1993).
[CrossRef]

Schmidt, B.

Shannon, P. J.

W. M. Gibbons, P. J. Shannon, S.-T. Sun, B. J. SwetlinNature (London) 351, 49 (1991).
[CrossRef]

Sun, S.-T.

W. M. Gibbons, P. J. Shannon, S.-T. Sun, B. J. SwetlinNature (London) 351, 49 (1991).
[CrossRef]

Swetlin, B. J.

W. M. Gibbons, P. J. Shannon, S.-T. Sun, B. J. SwetlinNature (London) 351, 49 (1991).
[CrossRef]

Tiziani, H. J.

Ulrich, C.

Appl. Opt. (1)

J. Opt. Soc. Am. B (1)

Nature (2)

W. M. Gibbons, P. J. Shannon, S.-T. Sun, B. J. SwetlinNature (London) 351, 49 (1991).
[CrossRef]

T. Ikeda, T. Sasaki, K. IchimuraNature (London) 361, 428 (1993).
[CrossRef]

Opt. Lett (1)

I. C. Khoo, H. Li, Y. LiangOpt. Lett 19, 1723 (1994).
[CrossRef] [PubMed]

Opt. Lett. (1)

Rev. Sci. Instrum. (1)

For example, R. GreefRev. Sci. Instrum. 41, 532 (1970).
[CrossRef]

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Figures (5)

Fig. 1
Fig. 1

Experimental setup for nonlinear spatial filtering using an azo-dye-doped LC cell. Definitions of the polarization parameters are shown. NDF, neutral density filter; L1, collimator lens.

Fig. 2
Fig. 2

(a) Example of transient signals obtained by a photodetector at analyzer angles of 0°, 45°, and 90°; (b) the calculated values of the angle α and the phase difference δ. Angle α is related to induced dichroism and optical axis change. The input laser power was 600 μW.

Fig. 3
Fig. 3

Beam-power dependence of angle α and phase difference δ for steady-state modulation.

Fig. 4
Fig. 4

(a) Beam-power dependence of the transmitted intensities for analyzer angles of 0 and ±10° and (b) the same dependence calculated by assuming an insertion of a QWP whose fast axis is −4°. A calculated linear response for the analyzer angle of 0° is also shown in (a).

Fig. 5
Fig. 5

Filtered results: (a) input object (a photomask for the LC display panel) observed without the LC cell, (b) edge enhancement realized by insertion of a QWP with the fast axis parallel to the LC director and an analyzer angle of −10°, and (c) defect enhancement with the fast axis angle of QWP equal to −4° and the same analyzer angle as in (b). The input laser power was 700 μW.

Equations (3)

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I ( 0 ) = I avg ( 1 + cos 2 α cos 2 θ + sin 2 α cos δ sin 2 θ ) ,
α = 1 2 cos 1 [ I ( 0 ) I ( 90 ) I ( 0 ) + I ( 90 ) ] ,
δ = cos 1 { [ 2 I ( 45 ) I ( 0 ) + I ( 90 ) 1 ] 1 sin 2 α } .

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