Abstract

A method of forming a laser damage resistant wide-spectrum antireflective coating on fused silica and other glasses has been developed. The single-layer graded-index coating is deposited from a specific polymer solution which is converted to a porous SiO2 film. The size of the pores in the film is first reduced by heat treatment to prevent eventual UV scattering. Refractive-index gradation is achieved by grading this non-scattering porosity using a mild etching agent to a depth which is sufficient to smooth the density transition from air to the substrate glass. The resultant coating provides antireflectivity over the entire transmission range of silica extending to wavelengths as short as 250 nm. Laser damage thresholds as high as 9 J/cm2 at 350 nm have been demonstrated for this coating on fused silica substrates, which makes it particularly suitable for the optics of high-power lasers.

© 1984 Optical Society of America

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References

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    [CrossRef]
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  13. S. McLean, U.S. Patent2,639,999 (26May1953).
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    [CrossRef] [PubMed]
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1982

B. E. Yoldas, Appl. Opt. 21, 2960 (1982).
[CrossRef] [PubMed]

B. E. Yoldas, J. Non-Cryst. Solids 51, 105 (1982).
[CrossRef]

1980

W. H. Lowdermilk, D. Milam, Appl. Phys. Lett. 36, 891 (1980).
[CrossRef]

B. E. Yoldas, Appl. Opt. 19, 1425 (1980).
[CrossRef] [PubMed]

1979

B. E. Yoldas, T. W. O’Keeffe, Appl. Opt. 18, 3133 (1979).
[CrossRef] [PubMed]

T. H. Elmer, F. W. Martin, Am. Ceram. Soc. Bull. 58, 1092 (1979).

1976

1969

H. Schroeder, Phys. Thin Films 5, 87 (1969).

1966

R. Jacopsson, Prog. Opt. 5, 249 (1966).

1961

1956

1953

1942

H. Schroder, Glastech. Ber. 20, No. 6, 161 (1942).

1941

A. Smakula, Glastech. Ber. 19, No. 12, 377 (1941).

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

H. Shhroter, Ann. Phys. 39, 55 (1941).

1940

C. H. Cartwright, Phys. Rev. 57, 1060 (1940).

1939

K. B. Blodgett, Phys. Rev. 55, 391 (1939).
[CrossRef]

K. B. Blodgett, Phys. Rev. 55, 391 (1939).
[CrossRef]

1934

G. Bauer, Ann. Phys. 19, 434 (1934).
[CrossRef]

1927

M. P. Amy, Rev. Opt. 6, 305 (1927).

1916

F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 22 (1916).

1886

Lord Rayleigh, Proc. R. Soc. London 41, 275 (1886).
[CrossRef]

Amy, M. P.

M. P. Amy, Rev. Opt. 6, 305 (1927).

Bauer, G.

G. Bauer, Ann. Phys. 19, 434 (1934).
[CrossRef]

Blodgett, K. B.

K. B. Blodgett, Phys. Rev. 55, 391 (1939).
[CrossRef]

K. B. Blodgett, Phys. Rev. 55, 391 (1939).
[CrossRef]

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975), p. 55.

Cartwright, C. H.

C. H. Cartwright, Phys. Rev. 57, 1060 (1940).

Elmer, T. H.

T. H. Elmer, F. W. Martin, Am. Ceram. Soc. Bull. 58, 1092 (1979).

Goldberg, B.

Homer, H. J.

Jacopsson, R.

R. Jacopsson, Prog. Opt. 5, 249 (1966).

Jones, F. L.

Kollmorgen, F.

F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 22 (1916).

Lowdermilk, W. H.

W. H. Lowdermilk, D. Milam, Appl. Phys. Lett. 36, 891 (1980).
[CrossRef]

W. H. Lowdermilk, D. Milam, J. G. Wilder, presented at the Fifteenth Annual Boulder Damage Symposium, Boulder, Colo.,

Martin, F. W.

T. H. Elmer, F. W. Martin, Am. Ceram. Soc. Bull. 58, 1092 (1979).

McLean, S.

S. McLean, U.S. Patent2,639,999 (26May1953).

Milam, D.

W. H. Lowdermilk, D. Milam, Appl. Phys. Lett. 36, 891 (1980).
[CrossRef]

W. H. Lowdermilk, D. Milam, J. G. Wilder, presented at the Fifteenth Annual Boulder Damage Symposium, Boulder, Colo.,

Minot, M. J.

Monaco, S. F.

Nicoll, F. H.

F. H. Nicoll, F. E. Williams, U.S. Patent2,486,431 (1Nov.1949).

O’Keeffe, T. W.

Partlow, D. P.

B. E. Yoldas, D. P. Partlow, J. Non-Cryst. Solids, in press (1984).

Pendorf, R.

Rayleigh, Lord

Lord Rayleigh, Proc. R. Soc. London 41, 275 (1886).
[CrossRef]

Schroder, H.

H. Schroder, Glastech. Ber. 20, No. 6, 161 (1942).

Schroeder, H.

H. Schroeder, Phys. Thin Films 5, 87 (1969).

Shhroter, H.

H. Shhroter, Ann. Phys. 39, 55 (1941).

Smakula, A.

A. Smakula, Glastech. Ber. 19, No. 12, 377 (1941).

Taylor, H. D.

H. D. Taylor, in The Adjustment and Testing of Telescope Objectives, T. Book, Ed. (York, England, 1894), p. 109.

von Fraunhoefer, J.

J. von Fraunhoefer, in Gesammelte Schriften, E. Lommel, Ed. (Verlag der K. Akademie, Munich, 1888), p. 35.

Wilder, J. G.

W. H. Lowdermilk, D. Milam, J. G. Wilder, presented at the Fifteenth Annual Boulder Damage Symposium, Boulder, Colo.,

Williams, F. E.

F. H. Nicoll, F. E. Williams, U.S. Patent2,486,431 (1Nov.1949).

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975), p. 55.

Yoldas, B. E.

Am. Ceram. Soc. Bull.

T. H. Elmer, F. W. Martin, Am. Ceram. Soc. Bull. 58, 1092 (1979).

Ann. Phys.

H. Shhroter, Ann. Phys. 39, 55 (1941).

G. Bauer, Ann. Phys. 19, 434 (1934).
[CrossRef]

Appl. Opt.

Appl. Phys. Lett.

W. H. Lowdermilk, D. Milam, Appl. Phys. Lett. 36, 891 (1980).
[CrossRef]

Glastech. Ber.

H. Schroder, Glastech. Ber. 20, No. 6, 161 (1942).

A. Smakula, Glastech. Ber. 19, No. 12, 377 (1941).

J. Non-Cryst. Solids

B. E. Yoldas, J. Non-Cryst. Solids 51, 105 (1982).
[CrossRef]

J. Opt. Soc. Am.

Phys. Rev.

C. H. Cartwright, Phys. Rev. 57, 1060 (1940).

K. B. Blodgett, Phys. Rev. 55, 391 (1939).
[CrossRef]

K. B. Blodgett, Phys. Rev. 55, 391 (1939).
[CrossRef]

Phys. Thin Films

H. Schroeder, Phys. Thin Films 5, 87 (1969).

Proc. R. Soc. London

Lord Rayleigh, Proc. R. Soc. London 41, 275 (1886).
[CrossRef]

Prog. Opt.

R. Jacopsson, Prog. Opt. 5, 249 (1966).

Rev. Opt.

M. P. Amy, Rev. Opt. 6, 305 (1927).

Trans. Illum. Eng. Soc.

F. Kollmorgen, Trans. Illum. Eng. Soc. 11, 22 (1916).

Other

J. von Fraunhoefer, in Gesammelte Schriften, E. Lommel, Ed. (Verlag der K. Akademie, Munich, 1888), p. 35.

H. D. Taylor, in The Adjustment and Testing of Telescope Objectives, T. Book, Ed. (York, England, 1894), p. 109.

B. E. Yoldas, D. P. Partlow, J. Non-Cryst. Solids, in press (1984).

F. H. Nicoll, F. E. Williams, U.S. Patent2,486,431 (1Nov.1949).

S. McLean, U.S. Patent2,639,999 (26May1953).

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975), p. 55.

W. H. Lowdermilk, D. Milam, J. G. Wilder, presented at the Fifteenth Annual Boulder Damage Symposium, Boulder, Colo.,

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Figures (10)

Fig. 1
Fig. 1

Unfired coating thickness as a function of spin speed on 5-cm diam optically polished silica disks.

Fig. 2
Fig. 2

Unfired coating thickness on optically polished silica as a function of solution drain rate.

Fig. 3
Fig. 3

Profile taken across the interface between the uncoated polished silica substrate and the coated region. This sample was prepared by masking the left (uncoated) area of the substrate with Teflon tape during coating application. (The tape was removed before heat treatment.) The ridge at the edge of the coating represents a meniscus created at the tape boundary. Such profiles illustrate both coating smoothness and thickness.

Fig. 4
Fig. 4

Films of low reflectivity may show very poor transmission at short wavelengths due to scattering by the pores when they are graded without first decreasing their size.

Fig. 5
Fig. 5

Gradation of the initial pores (shown schematically as cylinders) by etching to a depth dg may cause surface pore enlargement that causes joining of pores (A). This is prevented by shrinking the initial pore diameter r0 to r 0 by a heat treatment before grading (B).

Fig. 6
Fig. 6

Film thickness decreases as spin application speed is increased and is further reduced during heat treatment and etching. Area I designates the unfired film thickness range, which, after firing and etching, translates to area II. Only films falling within area II show acceptable AR characteristics.

Fig. 7
Fig. 7

Thickness of a SiO2 coating deposited on optically polished fused silica as a function of application rate using the drain coating technique: (A) unfired films; (B) heat-treated films. Only films within region II show acceptable AR characteristics in the 350–1000-nm range.

Fig. 8
Fig. 8

Various stages in coating treatment: A, As-coated unfired film. Refractive index is ~1.38 due to the presence of OR and OH groups. The pure SiO2 analog would be ~1.23. B, pyrolyzed film (porosity, ≃40%; pore diameter, ≃2 nm). C, film with tailored pores (porosity, ≃19%; pore diameter, ≃1 nm). D, film with graded pores.

Fig. 9
Fig. 9

Transmission electron micrograph showing the cross section of a coating with graded porosity. An evaporated aluminum layer, shown here as a dark band, was applied over the coating for spatial reference. Above that is the epoxy mounting material.

Fig. 10
Fig. 10

Spectral transmission curves for a drain-coated fused silica substrate before and after gradation of the pores. Note that there is no deterioration in UV transmission of the graded coating curve. Reference curves for silica and air are also included.

Tables (2)

Tables Icon

Table I Reduction of Refractive Index by Inclusion of Nonscattering Porosity

Tables Icon

Table II Etch Concentrations and Times Which Result in Proper Gradation of Pores at 25°C

Equations (3)

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n p 2 + ( n 2 - 1 ) ( 1 - P ) + 1 ,
t 2 V s η 1 / 2 d · g ,
d g = ( l 2 - r 0 ) / tan α .

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