Abstract

Response properties of photoinduced gratings were studied in planar cells of liquid crystal doped with multiwalled carbon nanotubes. The grating formation time deduced from beam-coupling measurements was obtained to be ~30 ms. Absorption spectroscopy implies that the permanent gratings are associated with periodically distributed carbonaceous material adsorbed on the inner surfaces of the cell windows under prolonged illumination to the 514.5-nm beams, giving rise to the persistent light-induced modulation of the easy axis.

© 2002 Optical Society of America

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References

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Annu. Rev. Mater. Sci.

W. E. Moerner, A. Grunnet-Jepsen and C. L. Thompson, �??Photorefractive polymer,�?? Annu. Rev. Mater. Sci. 27, 585�??623 (1997).
[CrossRef]

G. P.Wiederrecht, �??Photorefractive liquid crystals,�?? Annu. Rev. Mater. Sci. 31, 139�??169 (2001).
[CrossRef]

Appl. Phys. Lett.

P. Pagliusi and G. Cipparrone, �??Surface-induced photorefractive-like effect in pure liquid crystals,�?? Appl. Phys. Lett. 80, 168�??170 (2002).
[CrossRef]

W. Lee and S.-L. Yeh, �??Optical amplification in nematics doped with carbon nanotubes,�?? Appl. Phys. Lett. 79, 4488�??4490 (2001).
[CrossRef]

Chem. Phys. Lett.

G. Chambers and H. J. Byrne, �??Raman spectroscopic study of excited states and photo-polymerisation of C60 from solution,�?? Chem. Phys. Lett. 302, 307�??311 (1999).
[CrossRef]

IEEE Quantum Electron.

I. C. Khoo, �??Orientational photorefractive effects in nematic liquid crystals films,�?? IEEE Quantum Electron. 32, 525�??534 (1996).
[CrossRef]

J. Appl. Phys.

H. Ono and N. Kawatsuki, �??High-performance photorefractivity in high- and low-molar-mass liquid crystal mixtures,�?? J. Appl. Phys. 85, 2482�??2487 (1999).
[CrossRef]

J. Exp. Theor. Phys. Lett.

E. V. Rudenko and A. V. Sukhov, �??Photoinduced electrical conductivity and photorefraction in a nematic liquid crystal,�?? J. Exp. Theor. Phys. Lett. 59, 142�??146 (1994).

J. Phys. Chem.

Y. Wang and L.-T. Cheng, �??Nonlinear optical properties of fullerenes and charge-transfer complexes of fullerenes,�?? J. Phys. Chem. 96, 1530�??1532 (1992).
[CrossRef]

Opt. Express

Opt. Lett.

Synth. Met.

K. Komorowska, A. Miniewicz and J. Parka, �??Holographic grating recording in large area photoconducting liquid crystal pane,�?? Synth. Met. 109, 189�??193 (2000).
[CrossRef]

Other

W. Lee and H.-C. Chen, �??Diffraction by photoinduced permanent gratings in nanotube-doped liquid crystals,�?? (submitted for publication).

H. J. Eichler, P. Günter and D.W. Pohl, Laser-Induced Dynamic Gratings (Springer, Berlin 1986).

P. M. Ajayan, �??Carbon Nanotubes,�?? in Nanostructured Materials and Nanotechnology, H. S. Nalwa, ed. (Academic Press, San Diego 2002), pp.329�??360.
[CrossRef]

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Figures (4)

Fig. 1.
Fig. 1.

A typical, normalized linear absorption spectrum of a colloidal solution of multiwalled carbon nanotubes dispersed in n-hexane against an n-hexane reference at room temperature. The spectrum is featureless and shows a weak continuum due to the scattering by the suspended particles.

Fig. 2.
Fig. 2.

Voltage dependence of the index-grating formation time of a nanotube-doped nematic film with a grating constant of 27 μm. The incident beams are 20 and 1 mW, ○ and 40 and 1 mW, ●. Inset, expanded scale for small formation time constants.

Fig. 3.
Fig. 3.

Micrographic image (×100) of a permanent index grating in a film of the nematic E7 doped with carbon nanotubes (top) in comparison with that of a commercialized transmission grating of 500 grooves / cm (bottom).

Fig. 4.
Fig. 4.

Linear absorption spectra of the LC cells before (dashed curves) and after (solid curves) 1.2-W/cm2 laser exposure at 514.5 nm for 20 minutes. (a) Pristine E7 and (b) nanotube-doped E7.

Equations (3)

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Λ = λ / 2 n sin ( α 2 ) λ / .
g ( t ) 1 = ( g 1 ) [ 1 exp ( t τ ) ] ,
τ d ~ γ / K [ ( π / d ) 2 + ( 2 π / Λ ) 2 ] ,

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