Abstract

Abstract

The use of holographic structures is promising for the realization of efficient systems in backlight applications for displays. By applying surface relief gratings on top of a side-lit lightguide we realize a backlight that avoids the use of color filters. The grating is used as a light outcoupling and color-separating element. The demands for this grating are stringent and calculations have been performed to meet them. A prototype backlight, including the grating structure, has been assembled and characterized. Results of experiments are discussed.

© 2007 Optical Society of America

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  1. S. Serak, N. Tabiryan and B. Zeldovich, "High-efficiency 1.5 ?m thick optical axis grating and its use for laser beam combining," Opt. Lett. 32, 169-171 (2007).
    [CrossRef]
  2. X. Wang, D. Wilson, R. Muller, P. Maker and D. Psaltis, "Liquid-crystal blazed-grating beam deflector," Appl. Opt. 39, 6545-6555 (2000).
    [CrossRef]
  3. D. Wright, E. Brasselet, J. Zyss, G. Langer and W. Kern, "Dye-doped organic distributed-feedback lasers with index and surface gratings: the role of pump polarization and molecular orientation," J. Opt. Soc. Am. B 21, 944-950 (2004).
    [CrossRef]
  4. R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
    [CrossRef]
  5. M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
    [CrossRef]
  6. J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
    [CrossRef]
  7. C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
    [CrossRef]
  8. 8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
    [CrossRef]
  9. D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).
  10. M. Xu, H. P. Urbach and D. K. G. de Boer, "Simulations of birefringent gratings as polarizing color separator in backlight for flat-panel displays," Opt. Express 15, 5789 (2007).
    [CrossRef] [PubMed]
  11. Y-S. Choi, J-S. Choi, J-H. Min, J-H. Kim, S-M. Lee, "Backlight unit for flat panel display and flat panel display apparatus having the same," U.S. patent application publication US2006/0285185 (Dec. 21, 2006).
  12. Grating solver development company. www.gsolver.com
  13. M. G. Moharam and T. K. Gaylord, "Rigorous coupled-wave analysis of planar-grating diffraction," J. Opt. Soc. Am. 71, 811 (1981).
    [CrossRef]
  14. AZ Electronic Materials. www.az-em.com
  15. ELDIM manufacturer of 2D photometers & colorimeters and Inspection systems. www.eldim.fr

2007 (2)

2006 (2)

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

2005 (1)

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

2004 (2)

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

D. Wright, E. Brasselet, J. Zyss, G. Langer and W. Kern, "Dye-doped organic distributed-feedback lasers with index and surface gratings: the role of pump polarization and molecular orientation," J. Opt. Soc. Am. B 21, 944-950 (2004).
[CrossRef]

2003 (1)

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

2000 (1)

1981 (1)

Bastiaansen, C. W. M.

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

Brasselet, E.

Broer, D. J.

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

Bunning, T. J.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

Caputo, R.

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

Chen, H.-X.

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

Colgan, E. G.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Cornelissen, H. J.

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

de Boer, D. K. G.

M. Xu, H. P. Urbach and D. K. G. de Boer, "Simulations of birefringent gratings as polarizing color separator in backlight for flat-panel displays," Opt. Express 15, 5789 (2007).
[CrossRef] [PubMed]

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

Escuti, M. J.

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

Gaylord, T. K.

He, G. S.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

Hornix, E. J.

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

Jak, M. J. J.

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

Jakubiak, R.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

Kang, J. W.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Kern, W.

Kim, D. Y.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Kim, J. P.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Kim, J.J.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Kim, K.-J.

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

Kim, M. J.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Koh, K.-N.

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

Langer, G.

Lee, J. S.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Lee, J.-H.

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

Maker, P.

Moharam, M. G.

Muller, R.

Nakano, D.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Natarajan, L.V.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

Nishikai, A.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Noguchi, M.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Numata, H.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Oh, M.-C.

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

Ono, S.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Prasad, P. N.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

Psaltis, D.

Sánchez, C.

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

Serak, S.

Singh, R.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Suzuki, M.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Tabiryan, N.

Taira, Y.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Tondiglia, V.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

Urbach, H. P.

Vaia, R. A.

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

van Heesch, C.

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

van Heesch, C. M.

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

Wang, X.

Wilson, D.

Wright, D.

Xu, M.

Yamada, F.

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

Yoo, S. J.

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

Zeldovich, B.

Zyss, J.

Appl. Opt. (1)

Appl. Phys. Lett. (4)

R. Jakubiak, L.V. Natarajan, V. Tondiglia, G. S. He, P. N. Prasad, T. J. Bunning and R. A. Vaia, "Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals," Appl. Phys. Lett. 85, 6095 (2004).
[CrossRef]

M.-C. Oh, K.-J. Kim, J.-H. Lee, H.-X. Chen, and K.-N. Koh, "Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration," Appl. Phys. Lett. 89, 251104 (2006).
[CrossRef]

J. W. Kang, M. J. Kim, J. P. Kim, S. J. Yoo, J. S. Lee, D. Y. Kim, and J.J. Kim "Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films," Appl. Phys. Lett. 82, 3823 (2003).
[CrossRef]

C. Sánchez, M. J. Escuti, C. van Heesch, C. W. M. Bastiaansen and D. J. Broer, "An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram," Appl. Phys. Lett. 87, 094101 (2005).
[CrossRef]

J. Opt. Soc. Am. (1)

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

Opt. Express (1)

Opt. Lett. (1)

Proc. SPIE (1)

D. K. G. de Boer, R. Caputo, H. J. Cornelissen, C. M. van Heesch, E. J. Hornix, M. J. J. Jak "Diffractive grating structures for colour-separating backlights," Proc. SPIE 6196, 241 (2006).

Other (5)

Y-S. Choi, J-S. Choi, J-H. Min, J-H. Kim, S-M. Lee, "Backlight unit for flat panel display and flat panel display apparatus having the same," U.S. patent application publication US2006/0285185 (Dec. 21, 2006).

Grating solver development company. www.gsolver.com

AZ Electronic Materials. www.az-em.com

ELDIM manufacturer of 2D photometers & colorimeters and Inspection systems. www.eldim.fr

8. Y. Taira, D. Nakano, H. Numata, A. Nishikai, S. Ono, F. Yamada, M. Suzuki, M. Noguchi, R. Singh, E. G. Colgan, "Low-power LCD using a novel optical system," SID 02 Digest 1313-1315 (2002); F. Yamada, S. Ono, Y. Taira, "Dual layered very thin flat surface micro prism array directly molded in an LCD cell," Eurodisplay 2002, 339-342 (2002).
[CrossRef]

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Figures (13)

Fig. 1.
Fig. 1.

Color-filterless display configuration including a grating structure. The grating on top of a lightguide separates incoming light into red, green and blue colors. A lens array put in front of the grating images the various beams on the LC layer forming an RGB pixel structure. The figure is not to scale: the pitch of the grating is of the order of visible wavelengths, Λ≈400nm while the pitch of the lens array is d≈800µm.

Fig. 2.
Fig. 2.

Light propagating inside the lightguide is restricted to angles of ±42° with the normal to the entrance facet of the guide due to refraction. The light rays that are incident on the grating will make angles between 48° and 90° with the normal to its surface. Due to the Lambertian intensity distribution of light entering the lightguide, light incident on the grating with small angles (close to 48°) is less intense than light incident with steeper angles (close to 90°).

Fig. 3.
Fig. 3.

Estimation of the number of diffraction orders coupled out by a diffraction grating and of angles that they form with the normal to it for different periods (700nm, 500nm, 300nm). In all cases the same incidence angle θinc=69° is considered.

Fig. 4.
Fig. 4.

Contour plots of the diffraction efficiency of the grating for the first diffraction order (sum of -1T and -1R) versus incidence angle θinc and wavelength λ. In a given row, the number above every plot indicates the depth L of the grating. (a) Λ=300nm; (b) Λ=400nm, (c) Λ=500nm. The red rectangles in the Figure indicate the intervals for the grating depth that gives a smooth, decreasing DE as function of incident angle simultaneously for all wavelengths of interest (450nm<λ<650nm).

Fig. 5.
Fig. 5.

Optimal backlight configuration. Light from opposite directions is diffracted by the grating and generates a symmetric RGBGR pattern which avoids color-mixing problems. The figure is not to scale: the pitch of the grating is of the order of visible wavelengths, Λ≈400nm while the pitch of the lens array is d≈800µm.

Fig. 6.
Fig. 6.

(a). Sketch of the whole process for the realization of grating structures; (b) Optical setup for making the holographic gratings; M, mirrors; L1, L2, lenses; I, aperture; P, polarizer beam splitter; HWP, half-wave plate; θc, recording beam angle; S, sample.

Fig. 7.
Fig. 7.

SEM picture of a typical structure obtained by holographic techniques with photoresist materials. The structure is highly regular by observing the sample both in cross-section (a) and in top view (b).

Fig. 8.
Fig. 8.

(a). SEM picture of the realized grating structure. The fringe spacing is about Λ=320nm and the thickness of the grating about L=210nm; (b) diffraction efficiency plot of the realized grating. Dots indicate experimental measurements while solid lines (red and blue curves) are the GSolver fits for the same structure. Theoretical values of the intensities for the 0R and -1R orders (magenta and green curves respectively) are also reported as a reference.

Fig. 9.
Fig. 9.

(a). Plot of the diffraction efficiency versus diffracted angle. Colored curves show the outcoupled beams from the lightguide in a red-green-blue-green-red sequence. Gray curves represent the behavior of the grating when the incoming beams have no angular constraints (i.e. all incident angles occur). Dashed rectangles show the overlap regions between outcoupled colors. (b). Plot of the diffraction angle versus incident angle for a grating with a periodicity Λ=320nm.

Fig. 10.
Fig. 10.

Rays inside the lightguide. The incident beam I is partly reflected by the grating (0R), partly diffracted in transmission (-1T) and partly diffracted in reflection (-1R). The diffracted reflected beam is reflected once more at the reflective layer put on the base of the lightguide and comes again to the grating (-1R(0R)). It diffracts in reflection again by the grating (-1R(-1R) into the same direction as the incident beam I. This behavior is verified for every beam I with incidence angle in the interval 48°<θinc<90° and for every wavelength of interest.

Fig. 11.
Fig. 11.

Geometry of the lens array in front of the pixels.

Fig. 12.
Fig. 12.

Measurement of angular distribution of the light outcoupled from the grating. Some color overlap can be observed in the picture as predicted in Fig. 9(a).

Fig. 13.
Fig. 13.

(a). Photograph of periodically striped pattern as produced by a microlens array put in front of the grating. The image shows the RGBGR sequence of stripes. (b). Gamut of the obtained display. Several groups of points correspond to the peaks present in the spectral range of our light source. The dashed triangle represents the gamut of a common LCD-TV display. (c). Spectrum of a CCFL lamp.

Equations (2)

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m λ = Λ ( n 2 sin θ dif n 1 sin θ inc )
Λ = λ 2 sin θ c

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