Abstract

Results are reported on the experimental observation and detailed treatment of photoinduced dc currents, which arise in both dye-doped polymer and dispersion of liquid-crystalline droplets in the same polymer under cw laser-beam illumination. These currents reveal transient behavior, i.e., a relaxation to zero value after an initial increase. This growth is monotonic by low values of the laser radiation intensity, but it changes to oscillating behavior by higher values. A preliminary theoretical approach, which is based on experimentally observed features, reveals good qualitative agreement with current temporal-envelope measurements. The observation of these photoinduced currents is another evidence for the photorefractive nature of the light-induced diffraction gratings, which were observed earlier in the same materials.

© 2001 Optical Society of America

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References

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  1. P. Gunter and J.-P. Huignard, Photorefractive Materials and Their Applications (Springer-Verlag, Berlin, 1989), Vols. I and II.
  2. P. Yeh, Introduction to Photorefractive Nonlinear Optics (Wiley, New York, 1993).
  3. W. E. Moerner and S. M. Silence, “Polymeric photorefractive materials,” Chem. Rev. 94, 127–155 (1994); J. C. Scott, L. Th. Pautmeier, and W. E. Moerner, “Photoconductivity studies of photorefractive polymers,” J. Opt. Soc. Am. B 9, 2059–2064 (1992), and reference therein.
    [CrossRef]
  4. G. Cipparrone, A. Mazzulla, and F. Simoni, “Orientational gratings in dye doped polymer dispersed liquid crystals induced by photorefractive effect,” Opt. Lett. 23, 1505–1507 (1998); F. Simoni, G. Cipparrone, A. Mazzulla, and P. Pagliusi, “Polymer dispersed liquid crystals: effects of photorefractivity and local heating on holographic recording,” Chem. Phys. 245, 429–436 (1999), and reference therein.
    [CrossRef]
  5. G. Cipparrone, A. Mazzulla, and F. Simoni, “Writing and erasure of holographic gratings in dye doped PDLC,” Mol. Cryst. Liq. Cryst. 299, 329–336 (1997).
    [CrossRef]
  6. G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
    [CrossRef]
  7. J.-P. Huignard and A. Marrakchi, “Coherent signal beam amplification in two wave mixing experiments with photorefractive Bi12SiO20 crystals,” Opt. Commun. 38, 249–254 (1981).
    [CrossRef]
  8. P. S. Drzaic, Liquid Crystal Dispersions (World Scientific, Singapore, 1995).
  9. P. G. DeGennes and J. Prost, The Physics of Liquid Crystals 2nd ed. (Oxford University, London, 1993).

1998 (1)

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

1997 (1)

G. Cipparrone, A. Mazzulla, and F. Simoni, “Writing and erasure of holographic gratings in dye doped PDLC,” Mol. Cryst. Liq. Cryst. 299, 329–336 (1997).
[CrossRef]

1981 (1)

J.-P. Huignard and A. Marrakchi, “Coherent signal beam amplification in two wave mixing experiments with photorefractive Bi12SiO20 crystals,” Opt. Commun. 38, 249–254 (1981).
[CrossRef]

Cipparrone, G.

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

G. Cipparrone, A. Mazzulla, and F. Simoni, “Writing and erasure of holographic gratings in dye doped PDLC,” Mol. Cryst. Liq. Cryst. 299, 329–336 (1997).
[CrossRef]

Huignard, J.-P.

J.-P. Huignard and A. Marrakchi, “Coherent signal beam amplification in two wave mixing experiments with photorefractive Bi12SiO20 crystals,” Opt. Commun. 38, 249–254 (1981).
[CrossRef]

Lucchetti, L.

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

Marrakchi, A.

J.-P. Huignard and A. Marrakchi, “Coherent signal beam amplification in two wave mixing experiments with photorefractive Bi12SiO20 crystals,” Opt. Commun. 38, 249–254 (1981).
[CrossRef]

Mazzulla, A.

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

G. Cipparrone, A. Mazzulla, and F. Simoni, “Writing and erasure of holographic gratings in dye doped PDLC,” Mol. Cryst. Liq. Cryst. 299, 329–336 (1997).
[CrossRef]

Nicoletta, F. P.

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

Simoni, F.

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

G. Cipparrone, A. Mazzulla, and F. Simoni, “Writing and erasure of holographic gratings in dye doped PDLC,” Mol. Cryst. Liq. Cryst. 299, 329–336 (1997).
[CrossRef]

Mol. Cryst. Liq. Cryst. (1)

G. Cipparrone, A. Mazzulla, and F. Simoni, “Writing and erasure of holographic gratings in dye doped PDLC,” Mol. Cryst. Liq. Cryst. 299, 329–336 (1997).
[CrossRef]

Opt. Commun. (2)

G. Cipparrone, A. Mazzulla, F. P. Nicoletta, L. Lucchetti, and F. Simoni, “Holographic grating formation in dye doped polymer dispersed liquid crystals,” Opt. Commun. 150, 297–304 (1998).
[CrossRef]

J.-P. Huignard and A. Marrakchi, “Coherent signal beam amplification in two wave mixing experiments with photorefractive Bi12SiO20 crystals,” Opt. Commun. 38, 249–254 (1981).
[CrossRef]

Other (6)

P. S. Drzaic, Liquid Crystal Dispersions (World Scientific, Singapore, 1995).

P. G. DeGennes and J. Prost, The Physics of Liquid Crystals 2nd ed. (Oxford University, London, 1993).

P. Gunter and J.-P. Huignard, Photorefractive Materials and Their Applications (Springer-Verlag, Berlin, 1989), Vols. I and II.

P. Yeh, Introduction to Photorefractive Nonlinear Optics (Wiley, New York, 1993).

W. E. Moerner and S. M. Silence, “Polymeric photorefractive materials,” Chem. Rev. 94, 127–155 (1994); J. C. Scott, L. Th. Pautmeier, and W. E. Moerner, “Photoconductivity studies of photorefractive polymers,” J. Opt. Soc. Am. B 9, 2059–2064 (1992), and reference therein.
[CrossRef]

G. Cipparrone, A. Mazzulla, and F. Simoni, “Orientational gratings in dye doped polymer dispersed liquid crystals induced by photorefractive effect,” Opt. Lett. 23, 1505–1507 (1998); F. Simoni, G. Cipparrone, A. Mazzulla, and P. Pagliusi, “Polymer dispersed liquid crystals: effects of photorefractivity and local heating on holographic recording,” Chem. Phys. 245, 429–436 (1999), and reference therein.
[CrossRef]

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Figures (5)

Fig. 1
Fig. 1

Experimental setup to measure the photocurrent.

Fig. 2
Fig. 2

Effect of illumination (a) by a 37-W/cm2 temporal intensity step on the time dependence of the photocurrent for (b) a PDLC sample and (c) a polymer sample.

Fig. 3
Fig. 3

Same as Fig. 2 but for a higher laser-intensity value, I=130 W/cm2.

Fig. 4
Fig. 4

Peak current values (filled squares) versus the incident laser-beam intensity for (a) PDLC and (b) polymer samples. The continuous curves represent the numerical fit.

Fig. 5
Fig. 5

Scheme of the intensity variation along the z direction.

Equations (4)

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dhν0d*dT*d hν0d-+p+.
wc=αNI2,
n+t+γn++z -D n+z+Eμn+=αI2(z)N(z),
J(t)=-2χDeSN0αI02γ[(αI02t-1)exp(-αI02t)+exp(-γt)].

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