Abstract

We present an optically isotropic switchable microlens array (MLA) based on liquid crystals (LCs) using the Joule heating electrode structure. The LC molecules were initially aligned vertically on the lens and electrode surfaces. By applying voltage to the transparent electrodes, the temperature of the LC layer could be changed. Above the clearing point temperature of LCs, the LC layer shows an averaged refractive index that differs from the nematic state refractive index. The MLA could have switching characteristics by index matching between the LC layer and polymer lens structure. The proposed switchable MLA shows high light efficiency with truly optically isotropic properties.

© 2014 Optical Society of America

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References

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  1. T. Nose, S. Masuda, S. Stato, J. Li, L. C. Chien, and P. J. Bos, “Effect of low polymer content in a liquid crystal microlens,” Opt. Lett. 22, 351–353 (1997).
    [CrossRef]
  2. Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
    [CrossRef]
  3. M. Ferstl and A. Frisch, “Static and dynamic Fresnel zone lenses for optical interconnections,” J. Mod. Opt. 43, 1451–1462 (1996).
    [CrossRef]
  4. G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
    [CrossRef]
  5. J. S. Patel and K. Rastani, “Electrically controlled polarization-independent liquid-crystal Fresnel lens arrays,” Opt. Lett. 16, 532–534 (1991).
    [CrossRef]
  6. D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
    [CrossRef]
  7. Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
    [CrossRef]
  8. J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
    [CrossRef]
  9. J. S. Gwag, I.-Y. Han, C.-J. Yu, H. C. Choi, and J.-H. Kim, “Continuous viewing angle-tunable liquid crystal display using temperature-dependent birefringence layer,” Opt. Express 17, 5426–5432 (2009).
    [CrossRef]
  10. J. Li, S. Gauza, and S.-T. Wu, “Temperature effect on liquid crystal refractive indices,” J. Appl. Phys. 96, 19–24 (2004).
    [CrossRef]
  11. J. Li and S.-T. Wu, “Extended Cauchy equations for the refractive indices of liquid crystals,” J. Appl. Phys. 95, 896–901 (2004).
    [CrossRef]

2009 (1)

2007 (1)

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

2006 (1)

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

2005 (2)

Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
[CrossRef]

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

2004 (2)

J. Li, S. Gauza, and S.-T. Wu, “Temperature effect on liquid crystal refractive indices,” J. Appl. Phys. 96, 19–24 (2004).
[CrossRef]

J. Li and S.-T. Wu, “Extended Cauchy equations for the refractive indices of liquid crystals,” J. Appl. Phys. 95, 896–901 (2004).
[CrossRef]

1997 (1)

1996 (1)

M. Ferstl and A. Frisch, “Static and dynamic Fresnel zone lenses for optical interconnections,” J. Mod. Opt. 43, 1451–1462 (1996).
[CrossRef]

1991 (1)

1989 (1)

G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
[CrossRef]

Bos, P. J.

Chien, L. C.

Choi, H. C.

Choi, Y.

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
[CrossRef]

Clark, M. G.

G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
[CrossRef]

Ferstl, M.

M. Ferstl and A. Frisch, “Static and dynamic Fresnel zone lenses for optical interconnections,” J. Mod. Opt. 43, 1451–1462 (1996).
[CrossRef]

Frisch, A.

M. Ferstl and A. Frisch, “Static and dynamic Fresnel zone lenses for optical interconnections,” J. Mod. Opt. 43, 1451–1462 (1996).
[CrossRef]

Gauza, S.

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

J. Li, S. Gauza, and S.-T. Wu, “Temperature effect on liquid crystal refractive indices,” J. Appl. Phys. 96, 19–24 (2004).
[CrossRef]

Gwag, J. S.

Han, I.-Y.

Kim, D.-W.

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

Kim, H.-R.

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

Kim, J.-H.

J. S. Gwag, I.-Y. Han, C.-J. Yu, H. C. Choi, and J.-H. Kim, “Continuous viewing angle-tunable liquid crystal display using temperature-dependent birefringence layer,” Opt. Express 17, 5426–5432 (2009).
[CrossRef]

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
[CrossRef]

Kim, S.-J.

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

Kim, Y.-T.

Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
[CrossRef]

Lee, K.-H.

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

Lee, S.-D.

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
[CrossRef]

Lee, Y.-M.

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

Li, J.

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

J. Li, S. Gauza, and S.-T. Wu, “Temperature effect on liquid crystal refractive indices,” J. Appl. Phys. 96, 19–24 (2004).
[CrossRef]

J. Li and S.-T. Wu, “Extended Cauchy equations for the refractive indices of liquid crystals,” J. Appl. Phys. 95, 896–901 (2004).
[CrossRef]

T. Nose, S. Masuda, S. Stato, J. Li, L. C. Chien, and P. J. Bos, “Effect of low polymer content in a liquid crystal microlens,” Opt. Lett. 22, 351–353 (1997).
[CrossRef]

Lu, R.

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

Masuda, S.

Nose, T.

Patel, J. S.

Powell, N. J.

G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
[CrossRef]

Purvis, A.

G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
[CrossRef]

Rastani, K.

Stato, S.

Wen, C.-H.

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

Williams, G.

G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
[CrossRef]

Wu, S.-T.

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

J. Li, S. Gauza, and S.-T. Wu, “Temperature effect on liquid crystal refractive indices,” J. Appl. Phys. 96, 19–24 (2004).
[CrossRef]

J. Li and S.-T. Wu, “Extended Cauchy equations for the refractive indices of liquid crystals,” J. Appl. Phys. 95, 896–901 (2004).
[CrossRef]

Yu, C.-J.

J. S. Gwag, I.-Y. Han, C.-J. Yu, H. C. Choi, and J.-H. Kim, “Continuous viewing angle-tunable liquid crystal display using temperature-dependent birefringence layer,” Opt. Express 17, 5426–5432 (2009).
[CrossRef]

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

Appl. Phys. Lett. (2)

Y. Choi, H.-R. Kim, K.-H. Lee, Y.-M. Lee, and J.-H. Kim, “A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer,” Appl. Phys. Lett. 91, 221113 (2007).
[CrossRef]

D.-W. Kim, C.-J. Yu, H.-R. Kim, S.-J. Kim, and S.-D. Lee, “Polarization-insensitivity liquid crystal Fresnel lens of dynamic focusing in an orthogonal binary configuration,” Appl. Phys. Lett. 88, 203505 (2006).
[CrossRef]

J. Appl. Phys. (2)

J. Li, S. Gauza, and S.-T. Wu, “Temperature effect on liquid crystal refractive indices,” J. Appl. Phys. 96, 19–24 (2004).
[CrossRef]

J. Li and S.-T. Wu, “Extended Cauchy equations for the refractive indices of liquid crystals,” J. Appl. Phys. 95, 896–901 (2004).
[CrossRef]

J. Dispersion Sci. Technol. (1)

J. Li, C.-H. Wen, S. Gauza, R. Lu, and S.-T. Wu, “Refractive indices of liquid crystals for display applications,” J. Dispersion Sci. Technol. 1, 51–61 (2005).
[CrossRef]

J. Mod. Opt. (1)

M. Ferstl and A. Frisch, “Static and dynamic Fresnel zone lenses for optical interconnections,” J. Mod. Opt. 43, 1451–1462 (1996).
[CrossRef]

Mol. Cryst. Liq. Cryst. (1)

Y. Choi, Y.-T. Kim, S.-D. Lee, and J.-H. Kim, “Polarization independent static microlens array in the homeotropic liquid crystal configuration,” Mol. Cryst. Liq. Cryst. 433, 191–197 (2005).
[CrossRef]

Opt. Express (1)

Opt. Lett. (2)

Proc. SPIE (1)

G. Williams, N. J. Powell, A. Purvis, and M. G. Clark, “Electrically controllable liquid crystal Fresnel lens,” Proc. SPIE 1168, 352–359 (1989).
[CrossRef]

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Figures (6)

Fig. 1.
Fig. 1.

Operating principle for the proposed MLA system.

Fig. 2.
Fig. 2.

SEM image and surface profile of an MLA structure.

Fig. 3.
Fig. 3.

Temperature characteristics as a function of applied voltage.

Fig. 4.
Fig. 4.

Temperature-dependent refractive indices of 5CB LC at a wavelength of 589 nm. Triangles and circles represent experimental data, and solid lines were fit using the Wu model.

Fig. 5.
Fig. 5.

Microscopic images of focused beam patterns at (a) 28°C and (b) 45°C. (c) Spatial light intensity profiles at the focal plane.

Fig. 6.
Fig. 6.

Normalized beam intensity of the proposed MLA at the focal point as a function of the polarization state of incident light.

Equations (4)

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na=(ne+2no)/3.
neabT+(2/3)Δn(0)(1T/Tc)β,
n0abT(1/3)Δn(0)(1T/Tc)β,
f=R/(nlcnp),

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