Abstract

Attention is drawn to the properties of Ta2O5 film which make it attractive as a new dielectric medium for use in integrated optical circuitry. The Ta2O5 film discussed was formed by thermally oxidizing sputtered β-tantalum films in an oxygen atmosphere. Measurements showed that these films will support propagation of coherent red (6328-Å.) light with a loss of 0.9 dB cm−1 and coherent blue (4880-Å) light with a somewhat higher loss of 4.1 dB cm−1. From measurements of the coupling angle at which propagation of the various modes takes place, refractive indices for the TE and TM modes at 6328 Å, 5145 Å, and 4880 Å were obtained. The loss mechanisms are discussed, and it is shown that most of the loss is due to scattering during the internal reflections at the air–oxide and oxide–substrate film surfaces. A small fraction of the loss appears to occur in the interior of the film. With Ta2O5 it is demonstrated for the first time that optical circuit components can be formed for use in integrated optics by employing existing thin-film technology. The basic process steps include the pattern generation of the β-Ta followed by thermal oxidation of the pattern. Experimental studies of propagation in straight and curved waveguides are described. It was found that the losses in pattern generated waveguides are of the order of 5 dB cm−1 to 7 dB cm−1, with the excess loss due to scattering from the waveguide edges. It is concluded that improvements in the smoothness of the boundaries of circuit elements are desirable to reduce transmission losses in pattern generated film.

© 1971 Optical Society of America

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References

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  1. S. E. Miller, Bell Syst. Tech. J. 48, 2059 (1969).
  2. E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2071 (1969).
  3. J. E. Goell, Bell Syst. Tech. J. 48, 2133 (1969).
  4. J. E. Goell, R. D. Standley, Bell Syst. Tech. J. 48, 3445 (1969).
  5. P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
    [CrossRef]
  6. D. G. Muth, J. Vacuum Sci. Technol. 6, 749 (1969).
    [CrossRef]
  7. D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
    [CrossRef]
  8. D. Marcuse, Bell Syst. Tech. J. 48, 3187 (1969).
  9. R. W. Berry, P. M. Hall, M. T. Harris, in Thin Film Technology (Van Nostrand, Princeton, N. J., 1968), Chap. 10.
  10. E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2103 (1969).
  11. J. E. Goell, R. D. Standley, Proc. IEEE 58, 1504 (1969).
    [CrossRef]

1969 (10)

S. E. Miller, Bell Syst. Tech. J. 48, 2059 (1969).

E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2071 (1969).

J. E. Goell, Bell Syst. Tech. J. 48, 2133 (1969).

J. E. Goell, R. D. Standley, Bell Syst. Tech. J. 48, 3445 (1969).

P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
[CrossRef]

D. G. Muth, J. Vacuum Sci. Technol. 6, 749 (1969).
[CrossRef]

D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
[CrossRef]

D. Marcuse, Bell Syst. Tech. J. 48, 3187 (1969).

E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2103 (1969).

J. E. Goell, R. D. Standley, Proc. IEEE 58, 1504 (1969).
[CrossRef]

Aladjem, A.

D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
[CrossRef]

Berry, R. W.

R. W. Berry, P. M. Hall, M. T. Harris, in Thin Film Technology (Van Nostrand, Princeton, N. J., 1968), Chap. 10.

Brandon, D. G.

D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
[CrossRef]

Goell, J. E.

J. E. Goell, Bell Syst. Tech. J. 48, 2133 (1969).

J. E. Goell, R. D. Standley, Bell Syst. Tech. J. 48, 3445 (1969).

J. E. Goell, R. D. Standley, Proc. IEEE 58, 1504 (1969).
[CrossRef]

Hall, P. M.

R. W. Berry, P. M. Hall, M. T. Harris, in Thin Film Technology (Van Nostrand, Princeton, N. J., 1968), Chap. 10.

Harris, M. T.

R. W. Berry, P. M. Hall, M. T. Harris, in Thin Film Technology (Van Nostrand, Princeton, N. J., 1968), Chap. 10.

Marcatili, E. A. J.

E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2103 (1969).

E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2071 (1969).

Marcuse, D.

D. Marcuse, Bell Syst. Tech. J. 48, 3187 (1969).

Martin, R. J.

P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
[CrossRef]

Miller, S. E.

S. E. Miller, Bell Syst. Tech. J. 48, 2059 (1969).

Muth, D. G.

D. G. Muth, J. Vacuum Sci. Technol. 6, 749 (1969).
[CrossRef]

Standley, R. D.

J. E. Goell, R. D. Standley, Bell Syst. Tech. J. 48, 3445 (1969).

J. E. Goell, R. D. Standley, Proc. IEEE 58, 1504 (1969).
[CrossRef]

Tien, P. K.

P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
[CrossRef]

Ulrich, R.

P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
[CrossRef]

Yahalom, J.

D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
[CrossRef]

Zahavi, J.

D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
[CrossRef]

Appl. Phys. Lett. (1)

P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
[CrossRef]

Bell Syst. Tech. J. (6)

D. Marcuse, Bell Syst. Tech. J. 48, 3187 (1969).

S. E. Miller, Bell Syst. Tech. J. 48, 2059 (1969).

E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2071 (1969).

J. E. Goell, Bell Syst. Tech. J. 48, 2133 (1969).

J. E. Goell, R. D. Standley, Bell Syst. Tech. J. 48, 3445 (1969).

E. A. J. Marcatili, Bell Syst. Tech. J. 48, 2103 (1969).

J. Vacuum Sci. Technol. (2)

D. G. Muth, J. Vacuum Sci. Technol. 6, 749 (1969).
[CrossRef]

D. G. Brandon, J. Zahavi, A. Aladjem, J. Yahalom, J. Vacuum Sci. Technol. 6, 783 (1969).
[CrossRef]

Proc. IEEE (1)

J. E. Goell, R. D. Standley, Proc. IEEE 58, 1504 (1969).
[CrossRef]

Other (1)

R. W. Berry, P. M. Hall, M. T. Harris, in Thin Film Technology (Van Nostrand, Princeton, N. J., 1968), Chap. 10.

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Figures (8)

Fig. 1
Fig. 1

Propagation of red laser light (λ = 6328 Å) in the TE Ta2O5 film. The glass slide is approximately 0.6 in. mode in a (1.5 cm) wide and 3 in. (7.6 cm) long.

Fig. 2
Fig. 2

Scattered intensity vs streak length for the film shown in Fig. 1. The line is a least-squares computer fit to the data. The slope of the computer fit yields α = 0.103 cm−1 (or 0.89 dB cm−1).

Fig. 3
Fig. 3

Measured attenuation coefficient as plotted against the calculated number of internal reflections suffered per centimeter length of film. The data are shown in Table II.

Fig. 4
Fig. 4

Electron beam photograph of a carbon replica of the surface of the Ta2O5 film shown in Fig. 1.

Fig. 5
Fig. 5

A schematic drawing of a light beam being launched into a waveguide, showing the synchronous angles θ3 and ϕ.

Fig. 6
Fig. 6

Propagation of red (λ = 6328 Å) light in a straight waveguide of Ta2O5 film 50 μ wide on a 2.5 cm by 7.6 cm glass substrate.

Fig. 7
Fig. 7

Propagation of red (λ = 6328 Å) light in a curved waveguide of Ta2O5 film 25 μ wide on a 2.5 cm by 7.6 cm glass substrate. The light is launched into a pad and coupled into the waveguide through a transition region.

Fig. 8
Fig. 8

Magnified view of a 25-μ wide Ta2O5 waveguide. The wavy and ragged nature of the edge illustrates the need for improved etching techniques.

Tables (2)

Tables Icon

Table I Comparison Between Observed and Theoretically Expected Propagation Constants of a Ta2O5 Film Showing the Polarization of the Light and the Refractive Index of the Film for Each Wavelength a

Tables Icon

Table II Attenuation Coefficient, Synchronous Angle, and Internal Reflections/cm for the Four TE Modes Propagated in the Ta2O5 Film Shown in Fig. I a

Equations (3)

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exp ( - i ω t ± i k x x ± i k y y + i k z z ) ,
n 3 sin θ 3 = n 1 sin θ 1 , k x = k n 1 sin θ 1 cos ϕ , k y = k n 1 sin θ 1 sin ϕ , k z = k n 1 cos θ 1 ,
k x 2 + k y 2 + k z 2 = k 2 n 1 2 ,

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