Abstract

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately ±10°. In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

© 1995 Optical Society of America

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References

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  1. See, e.g., many of the review papers in the special issue of the International Journal of Nonlinear Optical Physics, October 1993.
  2. S. T. Wu, “Design of a liquid-crystal-based electro-optic filter,” Appl. Opt. 28, 48–52 (1989).
    [CrossRef] [PubMed]
  3. J. Staromlynska, “Electro-optic broad band tunable filters using liquid crystals,” J. Mod. Opt. 37, 639–652 (1990).
    [CrossRef]
  4. F. C. Saunders, G. Parry, “Novel optical cell design for liquid crystal devices providing sub-millisecond switching,” Opt. Quantum Electron. 18, 426–430 (1986).
    [CrossRef]
  5. A. Berman, “Agile notch filters,” in Proceedings of the First DoD Liquid Crystal Workshop, J. G. Theodore, ed. (U.S. Air Force Wright-Patterson Laboratory, Dayton, Ohio, 1993), pp. 47–101.
  6. G. H. Heilmeier, L. A. Zanoni, “Guest-host interactions in nematic liquid crystals,” Appl. Phys. Lett. 13, 91–93 (1968).
    [CrossRef]
  7. S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
    [CrossRef]
  8. Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).
  9. S. T. Wu, “Film-compensated homeotropic liquid-crystal cell for direct view display,” J. Appl. Phys. 76, 5975–5980 (1994).
    [CrossRef]
  10. See, e.g., L. Levi, Applied Optics (Wiley, New York, 1980), Vol. 2, Chap. 11.
  11. I. C. Khoo, S. T. Wu, Optics and Nonlinear Optics of Liquid Crystals (World Scientific, Singapore, 1993), Chap. 2.
    [CrossRef]

1994

S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
[CrossRef]

S. T. Wu, “Film-compensated homeotropic liquid-crystal cell for direct view display,” J. Appl. Phys. 76, 5975–5980 (1994).
[CrossRef]

1991

Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).

1990

J. Staromlynska, “Electro-optic broad band tunable filters using liquid crystals,” J. Mod. Opt. 37, 639–652 (1990).
[CrossRef]

1989

1986

F. C. Saunders, G. Parry, “Novel optical cell design for liquid crystal devices providing sub-millisecond switching,” Opt. Quantum Electron. 18, 426–430 (1986).
[CrossRef]

1968

G. H. Heilmeier, L. A. Zanoni, “Guest-host interactions in nematic liquid crystals,” Appl. Phys. Lett. 13, 91–93 (1968).
[CrossRef]

Berman, A.

A. Berman, “Agile notch filters,” in Proceedings of the First DoD Liquid Crystal Workshop, J. G. Theodore, ed. (U.S. Air Force Wright-Patterson Laboratory, Dayton, Ohio, 1993), pp. 47–101.

Fujimura, Y.

Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).

Fung, B. M.

S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
[CrossRef]

Heilmeier, G. H.

G. H. Heilmeier, L. A. Zanoni, “Guest-host interactions in nematic liquid crystals,” Appl. Phys. Lett. 13, 91–93 (1968).
[CrossRef]

Ho, M. S.

S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
[CrossRef]

Khoo, I. C.

I. C. Khoo, S. T. Wu, Optics and Nonlinear Optics of Liquid Crystals (World Scientific, Singapore, 1993), Chap. 2.
[CrossRef]

Levi, L.

See, e.g., L. Levi, Applied Optics (Wiley, New York, 1980), Vol. 2, Chap. 11.

Margerum, J. D.

S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
[CrossRef]

Nagatsuka, T.

Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).

Parry, G.

F. C. Saunders, G. Parry, “Novel optical cell design for liquid crystal devices providing sub-millisecond switching,” Opt. Quantum Electron. 18, 426–430 (1986).
[CrossRef]

Saunders, F. C.

F. C. Saunders, G. Parry, “Novel optical cell design for liquid crystal devices providing sub-millisecond switching,” Opt. Quantum Electron. 18, 426–430 (1986).
[CrossRef]

Shimomura, T.

Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).

Staromlynska, J.

J. Staromlynska, “Electro-optic broad band tunable filters using liquid crystals,” J. Mod. Opt. 37, 639–652 (1990).
[CrossRef]

Wu, S. T.

S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
[CrossRef]

S. T. Wu, “Film-compensated homeotropic liquid-crystal cell for direct view display,” J. Appl. Phys. 76, 5975–5980 (1994).
[CrossRef]

S. T. Wu, “Design of a liquid-crystal-based electro-optic filter,” Appl. Opt. 28, 48–52 (1989).
[CrossRef] [PubMed]

I. C. Khoo, S. T. Wu, Optics and Nonlinear Optics of Liquid Crystals (World Scientific, Singapore, 1993), Chap. 2.
[CrossRef]

Yoshimi, H.

Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).

Zanoni, L. A.

G. H. Heilmeier, L. A. Zanoni, “Guest-host interactions in nematic liquid crystals,” Appl. Phys. Lett. 13, 91–93 (1968).
[CrossRef]

Appl. Opt.

Appl. Phys. Lett.

G. H. Heilmeier, L. A. Zanoni, “Guest-host interactions in nematic liquid crystals,” Appl. Phys. Lett. 13, 91–93 (1968).
[CrossRef]

S. T. Wu, J. D. Margerum, M. S. Ho, B. M. Fung, “Liquid crystal dyes with high solubility and large dielectric anisotropy,” Appl. Phys. Lett. 64, 2191–2193 (1994).
[CrossRef]

J. Appl. Phys.

S. T. Wu, “Film-compensated homeotropic liquid-crystal cell for direct view display,” J. Appl. Phys. 76, 5975–5980 (1994).
[CrossRef]

J. Mod. Opt.

J. Staromlynska, “Electro-optic broad band tunable filters using liquid crystals,” J. Mod. Opt. 37, 639–652 (1990).
[CrossRef]

Opt. Quantum Electron.

F. C. Saunders, G. Parry, “Novel optical cell design for liquid crystal devices providing sub-millisecond switching,” Opt. Quantum Electron. 18, 426–430 (1986).
[CrossRef]

Soc. Inf. Displ., Technol. Dig.

Y. Fujimura, T. Nagatsuka, H. Yoshimi, T. Shimomura, “Optical properties of retardation films for STN-LCDs,” Soc. Inf. Displ., Technol. Dig. 22, 739–742 (1991).

Other

See, e.g., L. Levi, Applied Optics (Wiley, New York, 1980), Vol. 2, Chap. 11.

I. C. Khoo, S. T. Wu, Optics and Nonlinear Optics of Liquid Crystals (World Scientific, Singapore, 1993), Chap. 2.
[CrossRef]

A. Berman, “Agile notch filters,” in Proceedings of the First DoD Liquid Crystal Workshop, J. G. Theodore, ed. (U.S. Air Force Wright-Patterson Laboratory, Dayton, Ohio, 1993), pp. 47–101.

See, e.g., many of the review papers in the special issue of the International Journal of Nonlinear Optical Physics, October 1993.

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Figures (10)

Fig. 1
Fig. 1

Schematic configuration of a PC switchable polarizer: (a) the device works as a high-reflectivity mirror, (b) the device works as a linear polarizer.

Fig. 2
Fig. 2

Wavelength-dependent phase retardation of a quarter-wave achromatic retarder made of polymer films. Dots are experimental data.

Fig. 3
Fig. 3

Voltage-dependent transmission of a homeotropically aligned LC cell. Zero transmission means zero phase retardation, and 100% output represents an exact 90° phase retardation for that particular probing wavelength. Red, green, and blue laser lines were used to simulate the visible spectral range. A nearly 100% transmission for all wavelengths is achieved at ~16 Vrms.

Fig. 4
Fig. 4

Response of a homeotropically aligned LC polarization converter. The upper trace represents the intensity of the output beam (the zero line was adjusted to coincide with the time axis), and the lower trace is the voltage applied to the LC device. In the off state (zero voltage) the output light is cross polarized and no light is transmitted. As the LC cell is activated as a quarter-wave plate, nearly 100% of the input intensity is recovered. Time scale has 2 ms/div; measurement temperature T = 23 °C; and frequency of voltage bursts f = 10-kHz sine waves.

Fig. 5
Fig. 5

Configuration of a switchable dichroic polarizer. The polarizer is A, optically clear when the voltage is off and B, becomes a linear polarizer when the voltage is on.

Fig. 6
Fig. 6

Absorption spectrum of a 10-μm-thick, perpendicularly aligned ZLI-3094 LC cell at voltage-on (solid curves) and voltage-off (dotted curves) states.

Fig. 7
Fig. 7

Voltage-dependent transmission of an 8-μm, perpendicularly aligned ZLI-3094 cell. All three laser beams are linearly polarized. The extinction ratio is 100:1, measured between V = 0

Fig. 8
Fig. 8

Response time of a switchable polarizer that uses an 8-μm-thick ZLI-3094 LC cell with the following parameters: an unpolarized laser beam at λ = 633 nm and an operating temperature of T = 23 °C. The time line represents 0% transmission. The time scale has 200 ms/div., and the frequency of voltage bursts is f = 10-kHz sine waves.

Fig. 9
Fig. 9

Viewing-angle-dependent transmission of a 5-μm-thick LC polarizer. The LC is 3% C5 dye in ZLI-2806, the extinction ratio is 100:1 from 0 to 40 Vrms, and T = 23 °C.

Fig. 10
Fig. 10

Switching time of 3% C5 dye dissolved in ZLI-2806. Cell gap d = 5 μm, λ = 488 nm, and T = 23 °C. The time scale has 10 ms/div.; frequency of voltage bursts f = 10 kHz sine waves.

Equations (2)

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τ rise = τ 0 [ ( V / V th ) 2 - 1 ] ,
τ decay = τ 0 ( V b / V th ) 2 - 1 ,

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