Abstract

There is a large demand for Organic Light-Emitting Displays (OLEDs) with higher contrast, particularly for outdoor applications. We show that lowering the reflectance of OLEDs, which is required for increasing the contrast, can also lead to a reduction of their efficiency when a small microcavity effect is not maintained in their structure. We describe in details the design of high-contrast bottom-emitting OLEDs that have low reflectance but still maintain a small cavity effect for efficient emission.

© 2008 Optical Society of America

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References

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  1. B. Bahadur, "Display parameters and requirements," in Liquid Crystals: Applications and Uses, B. Bahadur, ed., (World Scientific, Singapore, 1991), p. 82.
  2. J. A. Dobrowolski, B. T. Sullivan, and R. C. Bajcar, "Optical interference, contrast-enhanced electroluminescent device," Appl. Opt. 31, 5988-5996 (1992).
    [CrossRef] [PubMed]
  3. J. Whitaker and B. K. Benson, Standard Handbook of Video and Television Engineering, (McGraw-Hill, 2003).
  4. K. R. Boff and J. E. Lincoln, eds., Engineering Data Compendium. Vol. 1. Human Perception and Performance, Harry G. Armstrong Aerospace Medical Research Laboratory, Wright-Patterson Air Force Base, Ohio, 1988.
  5. P. Anderson, Advance Display Technologies, JISC Technology & Standards Watch Report, August 2005; http://www.jisc.ac.uk/whatwedo/services/services_techwatch/techwatch/techwatch_reports_0503.aspx
  6. See for example G. Björk, "Modification of spontaneous emission rate in planar dielectric microcavity structures," Phys. Rev. A 44, 669-681 (1991).
    [CrossRef] [PubMed]
  7. S. D. Smith, "Design of multilayer filters by considering two effective interfaces," J. Opt. Soc. Am. 48, 43-50 (1958).
    [CrossRef]
  8. C. W. Tang and S. A. VanSlyke, "Organic electroluminescent diodes," Appl. Phys. Lett. 51, 913-915 (1987).
    [CrossRef]
  9. R. E. Slusher and C. Weisbuch, "Optical microcavities in condensed matter systems," Solid State Comm. 92, 149-158 (1994).
    [CrossRef]
  10. G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
    [CrossRef]
  11. V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
    [CrossRef]
  12. R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
    [CrossRef]
  13. See for example US Patent 6549335 "High durability circular polarizer for use with emissive displays" (2003).
  14. A. M. Nuijs and J. J. L. Horikx, "Diffraction and scattering at antiglare structures for display devices," Appl. Opt. 33, 4058-4068 (1994).
    [CrossRef] [PubMed]
  15. O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
    [CrossRef]
  16. A. N. Krasnov, "High-contrast organic light-emitting diodes on flexible substrates," Appl. Phys. Lett. 80, 3853-3855 (2002).
    [CrossRef]
  17. H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
    [CrossRef]
  18. J. A. Dobrowolski, "Versatile computer program for absorbing optical thin film systems," Appl. Opt. 20, 74-81 (1981).
    [CrossRef] [PubMed]
  19. S. A. VanSlyke. C. H. Chen and C. W. Tang, "Organic electroluminescent devices with improved stability," Appl. Phys. Lett. 69, 2160-2162 (1996).
    [CrossRef]
  20. F. Lemarquis and G. Marchand, "Analytical achromatic design of metal-dielectric absorbers," Appl. Opt. 38, 4876-4884 (1999).
    [CrossRef]
  21. H. A. Macleod, "A new approach in the design of metal-dielectric thin-film optical coatings," Optica Acta 25, 93-106 (1978).
    [CrossRef]
  22. F. Goos, "Durchlässigkeit und reflexionsvermögen dünner silberschichten von ultrarot bis ultraviolet," Zeitschrift für Physik A Hadrons and Nuclei, 106, 606-619 (1937).
  23. H. A. Macleod, Thin-Film Optical Filters, Institute of Physics Publishing, 2001.
    [CrossRef]
  24. E. D. Palik, ed., Handbook of Optical Constants of Solids, Vols. I and II (Academic, New York, 1985).
  25. WVASE32 software (J. A. Woollam Co., Lincolrn, NE).
  26. D. Poitras, D. Dalacu, X. Liu, J. Lefebvre, P. J. Poole, and R. L. Williams, "Luminescent devices with symmetrical and asymmetrical microcavity structures," 46th Annual Tech. Conf. Proc. 317-322 (2003).
  27. D. Roth, C. Py, H. Fukutani, P. Marshall, M. Popela, and D. Leong, "An Organic Digital Integrated Multiplexing Clock Display," 10th Canadian Semiconductor Technology Conference, Ottawa, Canada, August 13-17, 2001.
  28. C. Py, D. Poitras, C.-C. Kuo, and H. Fukutani, "High-contrast organic light emitting diodes with a partially absorbing anode," Opt. Lett. 33, 1126-1128 (2008).
    [CrossRef] [PubMed]

2008 (1)

2003 (1)

H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
[CrossRef]

2002 (2)

G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
[CrossRef]

A. N. Krasnov, "High-contrast organic light-emitting diodes on flexible substrates," Appl. Phys. Lett. 80, 3853-3855 (2002).
[CrossRef]

2000 (1)

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

1999 (1)

1998 (1)

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

1996 (2)

R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
[CrossRef]

S. A. VanSlyke. C. H. Chen and C. W. Tang, "Organic electroluminescent devices with improved stability," Appl. Phys. Lett. 69, 2160-2162 (1996).
[CrossRef]

1994 (2)

R. E. Slusher and C. Weisbuch, "Optical microcavities in condensed matter systems," Solid State Comm. 92, 149-158 (1994).
[CrossRef]

A. M. Nuijs and J. J. L. Horikx, "Diffraction and scattering at antiglare structures for display devices," Appl. Opt. 33, 4058-4068 (1994).
[CrossRef] [PubMed]

1992 (1)

1987 (1)

C. W. Tang and S. A. VanSlyke, "Organic electroluminescent diodes," Appl. Phys. Lett. 51, 913-915 (1987).
[CrossRef]

1981 (1)

1978 (1)

H. A. Macleod, "A new approach in the design of metal-dielectric thin-film optical coatings," Optica Acta 25, 93-106 (1978).
[CrossRef]

1958 (1)

1937 (1)

F. Goos, "Durchlässigkeit und reflexionsvermögen dünner silberschichten von ultrarot bis ultraviolet," Zeitschrift für Physik A Hadrons and Nuclei, 106, 606-619 (1937).

Aziz, H.

H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
[CrossRef]

Bajcar, R. C.

Bulovic, V.

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Burrows, P. E.

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Christou, V.

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

Dobrowolski, J. A.

Dobson, P. J.

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

Dodabalapur, A.

R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
[CrossRef]

Etchells, M.

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

Forrest, S. R.

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Fukutani, H.

Garbuzov, D. Z.

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Goos, F.

F. Goos, "Durchlässigkeit und reflexionsvermögen dünner silberschichten von ultrarot bis ultraviolet," Zeitschrift für Physik A Hadrons and Nuclei, 106, 606-619 (1937).

Grandin, H. M.

H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
[CrossRef]

Gu, G.

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Horikx, J. J. L.

Hwangbo, C. K.

G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
[CrossRef]

Jordan, R. H.

R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
[CrossRef]

Jung, B. Y.

G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
[CrossRef]

Khalfin, V. B.

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Krasnov, A. N.

A. N. Krasnov, "High-contrast organic light-emitting diodes on flexible substrates," Appl. Phys. Lett. 80, 3853-3855 (2002).
[CrossRef]

Kuo, C.-C.

Lee, G. J.

G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
[CrossRef]

Lemarquis, F.

Liew, Y.-F.

H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
[CrossRef]

Macleod, H. A.

H. A. Macleod, "A new approach in the design of metal-dielectric thin-film optical coatings," Optica Acta 25, 93-106 (1978).
[CrossRef]

Marchand, G.

Nuijs, A. M.

Poitras, D.

Popovic, Z. D.

H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
[CrossRef]

Py, C.

Renault, O.

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

Rothberg, L. J.

R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
[CrossRef]

Salata, O. V.

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

Slusher, R. E.

R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
[CrossRef]

R. E. Slusher and C. Weisbuch, "Optical microcavities in condensed matter systems," Solid State Comm. 92, 149-158 (1994).
[CrossRef]

Smith, S. D.

Sullivan, B. T.

Tang, C. W.

C. W. Tang and S. A. VanSlyke, "Organic electroluminescent diodes," Appl. Phys. Lett. 51, 913-915 (1987).
[CrossRef]

VanSlyke, S. A.

S. A. VanSlyke. C. H. Chen and C. W. Tang, "Organic electroluminescent devices with improved stability," Appl. Phys. Lett. 69, 2160-2162 (1996).
[CrossRef]

C. W. Tang and S. A. VanSlyke, "Organic electroluminescent diodes," Appl. Phys. Lett. 51, 913-915 (1987).
[CrossRef]

Weisbuch, C.

R. E. Slusher and C. Weisbuch, "Optical microcavities in condensed matter systems," Solid State Comm. 92, 149-158 (1994).
[CrossRef]

Yoon, J. S.

G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
[CrossRef]

Appl. Opt. (4)

Appl. Phys. Lett. (5)

R. H. Jordan, L. J. Rothberg, A. Dodabalapur, and R. E. Slusher, "Efficiency-enhancement of microcavity organic light-emitting diodes," Appl. Phys. Lett. 69, (1996)
[CrossRef]

A. N. Krasnov, "High-contrast organic light-emitting diodes on flexible substrates," Appl. Phys. Lett. 80, 3853-3855 (2002).
[CrossRef]

H. Aziz, Y.-F. Liew, H. M. Grandin, and Z. D. Popovic, "Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures," Appl. Phys. Lett. 83, 186-188 (2003).
[CrossRef]

C. W. Tang and S. A. VanSlyke, "Organic electroluminescent diodes," Appl. Phys. Lett. 51, 913-915 (1987).
[CrossRef]

S. A. VanSlyke. C. H. Chen and C. W. Tang, "Organic electroluminescent devices with improved stability," Appl. Phys. Lett. 69, 2160-2162 (1996).
[CrossRef]

J. Opt. Soc. Am. (1)

Jpn. J. Appl. Phys. (1)

G. J. Lee, B. Y. Jung, C. K. Hwangbo, and J. S. Yoon, "Photoluminescence characteristics in metal-distributed feedback-mirror microcavity containing luminescent polymer and filler," Jpn. J. Appl. Phys. 41, 5241 (2002).
[CrossRef]

Opt. Lett. (1)

Optica Acta (1)

H. A. Macleod, "A new approach in the design of metal-dielectric thin-film optical coatings," Optica Acta 25, 93-106 (1978).
[CrossRef]

Phys. Rev. B. (1)

V. Bulovic, V. B. Khalfin, G. Gu, P. E. Burrows, D. Z. Garbuzov, and S. R. Forrest, "Weak microcavity effects in organic light-emitting devices," Phys. Rev. B. 58, 3730 (1998)
[CrossRef]

Solid State Comm. (1)

R. E. Slusher and C. Weisbuch, "Optical microcavities in condensed matter systems," Solid State Comm. 92, 149-158 (1994).
[CrossRef]

Thin Solid Films (1)

O. Renault, O. V. Salata, M. Etchells, P. J. Dobson, and V. Christou, "A low reflectivity multilayer cathode for organic light-emitting diodes," Thin Solid Films 379, 195-198 (2000).
[CrossRef]

Zeitschrift für Physik A Hadrons and Nuclei (1)

F. Goos, "Durchlässigkeit und reflexionsvermögen dünner silberschichten von ultrarot bis ultraviolet," Zeitschrift für Physik A Hadrons and Nuclei, 106, 606-619 (1937).

Other (11)

H. A. Macleod, Thin-Film Optical Filters, Institute of Physics Publishing, 2001.
[CrossRef]

E. D. Palik, ed., Handbook of Optical Constants of Solids, Vols. I and II (Academic, New York, 1985).

WVASE32 software (J. A. Woollam Co., Lincolrn, NE).

D. Poitras, D. Dalacu, X. Liu, J. Lefebvre, P. J. Poole, and R. L. Williams, "Luminescent devices with symmetrical and asymmetrical microcavity structures," 46th Annual Tech. Conf. Proc. 317-322 (2003).

D. Roth, C. Py, H. Fukutani, P. Marshall, M. Popela, and D. Leong, "An Organic Digital Integrated Multiplexing Clock Display," 10th Canadian Semiconductor Technology Conference, Ottawa, Canada, August 13-17, 2001.

J. Whitaker and B. K. Benson, Standard Handbook of Video and Television Engineering, (McGraw-Hill, 2003).

K. R. Boff and J. E. Lincoln, eds., Engineering Data Compendium. Vol. 1. Human Perception and Performance, Harry G. Armstrong Aerospace Medical Research Laboratory, Wright-Patterson Air Force Base, Ohio, 1988.

P. Anderson, Advance Display Technologies, JISC Technology & Standards Watch Report, August 2005; http://www.jisc.ac.uk/whatwedo/services/services_techwatch/techwatch/techwatch_reports_0503.aspx

See for example G. Björk, "Modification of spontaneous emission rate in planar dielectric microcavity structures," Phys. Rev. A 44, 669-681 (1991).
[CrossRef] [PubMed]

B. Bahadur, "Display parameters and requirements," in Liquid Crystals: Applications and Uses, B. Bahadur, ed., (World Scientific, Singapore, 1991), p. 82.

See for example US Patent 6549335 "High durability circular polarizer for use with emissive displays" (2003).

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Figures (9)

Fig. 1.
Fig. 1.

Schematic view of a bottom-emission OLED showing its Fabry-Perot-like structure and the parameters used in Eq. (3).

Fig. 2.
Fig. 2.

Emission spectrum of Alq3. The curve was taken as representing I 0 inside the OLED emitting layer.

Fig. 3.
Fig. 3.

(a). Structure of a conventional bottom-emission OLED. (b) Reflectance and (c) emission of a conventional OLED (thin line), and of one with Rcathode =0 (thick line). (RD is the luminous reflectance, given by Eq.(2)).

Fig. 4.
Fig. 4.

Refractive index and nk/λ dispersion curves for a few metals.

Fig. 5.
Fig. 5.

Schematic view of a metal layer, surrounded by arbitrary materials (ρ12 and ρ23 can represent the reflection coefficient of multilayers, media 1 and 3 can be different).

Fig. 6.
Fig. 6.

Refractive indices and extinction coefficients (both given at a wavelength of 550nm) of several metals and semiconductor materials, as found in the literature. Some isovalue-curves of nk product are shown (most optical constants values are extracted from Palik [24] and from J.A. Woollam WVASE software [25]).

Fig. 7.
Fig. 7.

(a). OLED design. (b). Calculated reflectance (solid line) with the photopic curve (dash line) and the value of the luminous reflectance RD . (c). Refractive index profile (step) and irradiance profile inside the OLED, with the arrows showing the metal layers, and the thin interfacial emitting layer marked in black. (d). Calculated luminance of the OLED (solid line), compared to that of a conventional OLED [dash line; same as in Fig. 3(c)].

Fig. 8.
Fig. 8.

(a). OLED design. (b). Calculated reflectance (solid line) with the photopic curve (dash line) and the value of the luminous reflectance RD . (c). Refractive index profile (step) and irradiance profile inside the OLED, with the arrows showing the metal layers, and the thin interfacial emitting layer marked in black. (d). Calculated luminance of the OLED (solid line), compared to that of a conventional OLED [dash line; same as in Fig. 3(c)].

Fig. 9.
Fig. 9.

(a). Schematic bottom view of multi-segment OLED device with and without metal-dielectric AR. (b). Picture of such a device after fabrication. This device corresponds to the design presented in Fig. 8.

Tables (2)

Tables Icon

Table I. Typical values of luminance for different ambient light conditions and display devices [4, 5].

Tables Icon

Table II. Values of Contrast Ratio (Eq. 1) corresponding to different values of RD and Lambient (assuming LD =500 cd/m2).

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

C R = L on + R D L ambient L off + R D L ambient ,
R D = λ 1 λ 2 V ( λ ) · R ( λ ) · S ( λ ) d λ λ 1 λ 2 V ( λ ) · S ( λ ) d λ
I OLED ( λ ) = 1 N i = 1 N T anode , i [ 1 + R cathode , i + 2 R cathode , i cos ( 4 π z i cos θ in λ + φ cathode , i ) ] 1 + R cathode , i R anode , i 2 R cathode , i R anode , i cos ( φ cathode , i + φ anode , i + 4 π L cos θ in λ ) I 0 ( z i , λ ) ,
φ anode + φ cathode 2 2 π L cos θ λ = m π .
r = ρ 12 + ρ 23 exp ( 2 i β ) 1 + ρ 12 ρ 23 exp ( 2 i β ) ,
r = ρ 23 + ρ 12 exp ( 2 i β ) 1 + ρ 12 ρ 23 exp ( 2 i β ) ,
I abs = 2 π λ n k d E 2 γ ,

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