Abstract

Gradient refractive index antireflection films are produced by a chemical etch/leach process applied to glasses sensitized by a phase-separating heat treatment. The reflectance (two surfaces) is effectively reduced from ~ 8% to < 1/2% in the wavelength regime 0.35–2.5 μ. The broadband antireflection film consists of a single, porous, skeletal layer made up largely of silica. The optical properties of the film are shown to depend on the time, temperature parameters of the phase-separating heat treatment, as well as the time, temperature parameter of the film-forming etch/leach treatment. The properties of films produced under different process conditions are correlated in a fashion that suggests that progressively steeper refractive index gradients are obtained for samples phase separated and formed at higher temperatures. A number of applications for these films are suggested, including solar energy devices.

© 1976 Optical Society of America

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References

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  1. J. Fraunhofer, in Gesamelte Schriften, edited by F. Hommel, (Munich, 1887).
  2. F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 220 (1916).
  3. F. L. Jones and H. L. Homer, J. Opt. Soc. Am. 31, 34 (1941).
    [Crossref]
  4. H. Schroeder, Z. Tech. Phys. 22, 38, 75 (1941).
  5. F. H. Nicoll, RCA Rev. 6, 298 (1942).
  6. F. H. Nicoll and F. E. Williams, J. Opt. Soc. Am. 33, 434 (1943).
    [Crossref]
  7. S. M. Thomsen, RCA Rev. 12, 143 (1951).
  8. F. H. Nicoll, (RCA) US Patent # 2, 707, 899 (1955).
  9. S. M. Thomsen, (RCA) US Patent # 2, 490, 662 (1949).
  10. F. J. Nicoll, J. Opt. Soc. Am. 42, 241 (1952).
    [Crossref]
  11. L. Holland, The Properties of Glass Surfaces (Chapman and Hall, London, 1966), pp. 155, 165.
  12. W. Vogel, Structure and Crystallization of Glasses (Pergamon, New York, 1971), pp. 60–80.
  13. Gerald B. Carrier, (to be published).
  14. Sebastiano F. Monaco, “Reflectance of an Inhomogeneous Thin Film,” J. Opt. Soc. Am. 51, 280 (1961).
    [Crossref]

1961 (1)

1952 (1)

1951 (1)

S. M. Thomsen, RCA Rev. 12, 143 (1951).

1943 (1)

1942 (1)

F. H. Nicoll, RCA Rev. 6, 298 (1942).

1941 (2)

F. L. Jones and H. L. Homer, J. Opt. Soc. Am. 31, 34 (1941).
[Crossref]

H. Schroeder, Z. Tech. Phys. 22, 38, 75 (1941).

1916 (1)

F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 220 (1916).

Carrier, Gerald B.

Gerald B. Carrier, (to be published).

Fraunhofer, J.

J. Fraunhofer, in Gesamelte Schriften, edited by F. Hommel, (Munich, 1887).

Holland, L.

L. Holland, The Properties of Glass Surfaces (Chapman and Hall, London, 1966), pp. 155, 165.

Homer, H. L.

Jones, F. L.

Kollmorgen, F.

F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 220 (1916).

Monaco, Sebastiano F.

Nicoll, F. H.

F. H. Nicoll and F. E. Williams, J. Opt. Soc. Am. 33, 434 (1943).
[Crossref]

F. H. Nicoll, RCA Rev. 6, 298 (1942).

F. H. Nicoll, (RCA) US Patent # 2, 707, 899 (1955).

Nicoll, F. J.

Schroeder, H.

H. Schroeder, Z. Tech. Phys. 22, 38, 75 (1941).

Thomsen, S. M.

S. M. Thomsen, RCA Rev. 12, 143 (1951).

S. M. Thomsen, (RCA) US Patent # 2, 490, 662 (1949).

Vogel, W.

W. Vogel, Structure and Crystallization of Glasses (Pergamon, New York, 1971), pp. 60–80.

Williams, F. E.

J. Opt. Soc. Am. (4)

RCA Rev. (2)

F. H. Nicoll, RCA Rev. 6, 298 (1942).

S. M. Thomsen, RCA Rev. 12, 143 (1951).

Trans. Illum. Eng. Soc. (1)

F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 220 (1916).

Z. Tech. Phys. (1)

H. Schroeder, Z. Tech. Phys. 22, 38, 75 (1941).

Other (6)

J. Fraunhofer, in Gesamelte Schriften, edited by F. Hommel, (Munich, 1887).

F. H. Nicoll, (RCA) US Patent # 2, 707, 899 (1955).

S. M. Thomsen, (RCA) US Patent # 2, 490, 662 (1949).

L. Holland, The Properties of Glass Surfaces (Chapman and Hall, London, 1966), pp. 155, 165.

W. Vogel, Structure and Crystallization of Glasses (Pergamon, New York, 1971), pp. 60–80.

Gerald B. Carrier, (to be published).

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Figures (9)

FIG. 1
FIG. 1

Percent reflectance and transmittance of sample # 4 versus wavelength.

FIG. 2
FIG. 2

Percent reflectance at 0.70 μ versus film-forming reaction time. Reaction temperature = 45 °C, phase separation = 3 h at 600 °C.

FIG. 3
FIG. 3

Percent reflectance at 0.70 μ versus film-forming reaction time. Reaction temperature = 80 °C, phase separation = 3 h at 600 °C.

FIG. 4
FIG. 4

Percent reflectance and transmittance of sample # 36 versus wavelength.

FIG. 5
FIG. 5

Percent reflectance at 0.70 μ versus film-forming time. Reaction time = 80 °C, phase separation = 3 h at 630–638 °C.

FIG. 6
FIG. 6

Percent reflectance at 0.70 μ versus film-forming time. Reaction time =80 °C, phase separation = 3 h at 660 °C.

FIG. 7
FIG. 7

Over the edge electron micrographs of porous antireflection films as described in Table IV.

FIG. 8
FIG. 8

Geometrical representation of a thin inhomogeneous dielectric film whose refractive index changes exponentially and is surrounded by homogeneous dielectric media.14

FIG. 9
FIG. 9

Reflectance versus d/λ for gradient refractive index films where the gradient, Δn2, is made progressively larger.

Tables (4)

Tables Icon

TABLE I Film formation at 45 °C as a function of reaction time.

Tables Icon

TABLE II Film formation at 80 °C as a function of reaction time.

Tables Icon

TABLE III Film formation versus phase-separation heat treatment.

Tables Icon

TABLE IV Estimated film thickness as related to phase-separating heat treatment and film-reaction temperature.

Equations (3)

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R R * = ( n 1 n 3 P + n 2 n 2 Q ) 2 + ( n 1 n 2 T + n 2 n 3 S ) 2 ( n 1 n 3 P - n 2 n 2 Q ) 2 - ( n 1 n 2 T - n 2 n 3 S ) 2 ,
P = Y 0 ( α ) J 0 ( β ) - J 0 ( α ) Y 0 ( β ) , Q = J 1 ( α ) Y 1 ( β ) - Y 1 ( α ) J 1 ( β ) , T = Y 0 ( α ) J 1 ( β ) - J 0 ( α ) Y 1 ( β ) , S = Y 1 ( α ) J 0 ( β ) - J 1 ( α ) Y 0 ( β ) ,
α = 2 π n 2 ln ( n 2 / n 2 ) d λ , β = 2 π n 2 ln ( n 2 / n 2 ) d λ .