Abstract

With present-day refinements, thin film multilayers can be designed theoretically to meet virtually any reasonable filtering requirements. Often, when the optical properties are specified over very wide spectral regions the thicknesses of the various layers are not related in any simple way. The manufacture of such multilayers presents many difficulties. The tolerances on layer thickness and refractive indices in some designs are often very narrow. We have developed an optical method for the accurate control of layer thickness that involves the measurement of transmittance over a wide spectral region (400–1000 mm). This measurement is performed continuously during deposition by a rapid scanning monochromator. The accuracy of such a system depends on a precise knowledge of the indices of refraction that are produced during the multilayer deposition. In addition the structure of many optical thin films used for hard coatings departs considerably from the simple method that is traditionally used in optical coating designs. In the method we have developed to compensate for such discrepancies, optical inhomogeneity is included by assuming a linear refractive-index profile, determined by analyzing experimental results. These results are in agreement with other studies of structure.

© 1981 Optical Society of America

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References

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  1. B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 17, 1038 (1978).
    [CrossRef] [PubMed]
  2. B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 18, 3851 (1979).
    [PubMed]
  3. H. A. Macleod, Vacuum 27, 383 (1977).
    [CrossRef]
  4. M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
    [CrossRef]
  5. H. A. Macleod, Thin Film Optical Filters (Hilger, London, 1969); H. A. Macleod, Appl. Opt. 20, 82 (1981).
    [CrossRef] [PubMed]
  6. A. L. Bloom, Appl. Opt. 20, 66 (1981); E. Pelletier, M. Klapisch, P. Giacomo, Nouv. Rev. Opt. Appl. 5, 247 (1971); J. P. Borgogno, E. Pelletier, J. Opt. Soc. Am. 68, 964 (1978).
    [CrossRef] [PubMed]
  7. E. Pelletier, P. Roche, B. Vidal, Nouv. Rev. Opt. Appl. 7, 353 (1976).
    [CrossRef]
  8. E. Ritter, Physics of Thin Films (Academic, New York, 1975), Vol. 8; S. Ogura, H. A. Macleod, Thin Solid Films 34, 371 (1976).
    [CrossRef]
  9. Proceedings of the Eighth International Vacuum Congress, Sept. 22–26, 1980, Cannes, France Supplément ā la Revue “LeVide, les couches minces” no20′, Vol. 1, Thin Films, pp. 385–388.

1981 (1)

1979 (2)

B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 18, 3851 (1979).
[PubMed]

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

1978 (1)

1977 (1)

H. A. Macleod, Vacuum 27, 383 (1977).
[CrossRef]

1976 (1)

E. Pelletier, P. Roche, B. Vidal, Nouv. Rev. Opt. Appl. 7, 353 (1976).
[CrossRef]

Bloom, A. L.

Fornier, A.

Harris, M.

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

Macleod, H. A.

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

H. A. Macleod, Vacuum 27, 383 (1977).
[CrossRef]

H. A. Macleod, Thin Film Optical Filters (Hilger, London, 1969); H. A. Macleod, Appl. Opt. 20, 82 (1981).
[CrossRef] [PubMed]

Ogura, S.

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

Pelletier, E.

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 18, 3851 (1979).
[PubMed]

B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 17, 1038 (1978).
[CrossRef] [PubMed]

E. Pelletier, P. Roche, B. Vidal, Nouv. Rev. Opt. Appl. 7, 353 (1976).
[CrossRef]

Ritter, E.

E. Ritter, Physics of Thin Films (Academic, New York, 1975), Vol. 8; S. Ogura, H. A. Macleod, Thin Solid Films 34, 371 (1976).
[CrossRef]

Roche, P.

E. Pelletier, P. Roche, B. Vidal, Nouv. Rev. Opt. Appl. 7, 353 (1976).
[CrossRef]

Vidal, B.

B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 18, 3851 (1979).
[PubMed]

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

B. Vidal, A. Fornier, E. Pelletier, Appl. Opt. 17, 1038 (1978).
[CrossRef] [PubMed]

E. Pelletier, P. Roche, B. Vidal, Nouv. Rev. Opt. Appl. 7, 353 (1976).
[CrossRef]

Appl. Opt. (3)

Nouv. Rev. Opt. Appl. (1)

E. Pelletier, P. Roche, B. Vidal, Nouv. Rev. Opt. Appl. 7, 353 (1976).
[CrossRef]

Thin Solid Films (1)

M. Harris, H. A. Macleod, S. Ogura, E. Pelletier, B. Vidal, Thin Solid Films 57, 173 (1979).
[CrossRef]

Vacuum (1)

H. A. Macleod, Vacuum 27, 383 (1977).
[CrossRef]

Other (3)

H. A. Macleod, Thin Film Optical Filters (Hilger, London, 1969); H. A. Macleod, Appl. Opt. 20, 82 (1981).
[CrossRef] [PubMed]

E. Ritter, Physics of Thin Films (Academic, New York, 1975), Vol. 8; S. Ogura, H. A. Macleod, Thin Solid Films 34, 371 (1976).
[CrossRef]

Proceedings of the Eighth International Vacuum Congress, Sept. 22–26, 1980, Cannes, France Supplément ā la Revue “LeVide, les couches minces” no20′, Vol. 1, Thin Films, pp. 385–388.

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Figures (14)

Fig. 1
Fig. 1

Evolution of the function of merit actually recorded during the deposition of the first layer of the longwave pass filter described in the text. Discontinuities in the curve correspond to automatic changes of vertical scale, and the horizontal time scale of the diagram is reset to zero each time the right boundary is reached. One complete traversal of the diagram corresponds to 80 sec.

Fig. 2
Fig. 2

Comparison between predicted (full line) and measured (dotted line) transmittance of the filter after the deposition of layer one, which gave the function of merit recorded in Fig. 1.

Fig. 3
Fig. 3

The function of merit for layer four recorded during the same run as that in Fig. 1.

Fig. 4
Fig. 4

Comparison between predicted (full line) and measured (dotted line) transmittance after deposition of layer four.

Fig. 5
Fig. 5

As Fig. 1 but layer seven.

Fig. 6
Fig. 6

As Fig. 2 but layer seven.

Fig. 7
Fig. 7

As Fig. 1 but layer eight.

Fig. 8
Fig. 8

As Fig. 2 but layer eight.

Fig. 9
Fig. 9

Results measured at the conclusion of five successive attempts at producing the longwave pass filter compared with the expected theoretical profile.

Fig. 10
Fig. 10

Comparison between experimental (dotted line) and predicted (full line) results achieved during a second series of tests using results actually measured during the first series as predictions. The curves shown here are reproduced from the screen of the V D U at the conclusion of the final layer, and their agreement is typical of that obtained during the entire second series of tests.

Fig. 11
Fig. 11

Measured values9 of the refractive index of TiO2 layers deposited at different substrate temperatures. Values given are the mean indices of the layers, which also possessed an inhomogeneity of index not shown in the figure. These measurements were all made in air after deposition.

Fig. 12
Fig. 12

Transmittance actually measured during the deposition of a layer of TiO2 compared with that predicted using value of 2.2 for index of refraction. The thickness of the layer is ~3λ/4 at 550 nm.

Fig. 13
Fig. 13

Transmittance actually measured at a later stage of deposition of the same layer as in Fig. 12. Thickness is ~3λ/2 at 550 nm; for comparison a theoretical curve calculated using an index of refraction of 2.2 is also shown.

Fig. 14
Fig. 14

Transmittance actually measured at the instant of termination of the layer of Figs. 13 and 14 together with that measured ~30 sec after air admittance. Thickness at this stage is ~9λ/4 at 550 nm; again a theoretical curve using an index of 2.2 is shown for comparison.

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