Abstract

We demonstrate a new and simple method of forming light-guiding interconnections in an integrated optical circuit. This involves bridging the devices with a thin film having tapered ends that form naturally during the deposition process. Experiments show that there is no specific requirement for the thickness, refractive index, or relative position of the bridging film. A theory of composite waveguides provides an understanding of these interconnections.

© 1973 Optical Society of America

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References

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  1. H. Kogelnik, C. V. Shank, Appl. Phys. Lett. 18, 152 (1971).
    [Crossref]
  2. P. K. Tien, R. J. Martin, R. Wolfe, R. C. LeCraw, S. L. Blank, Appl. Phys. Lett. 21, 394 (1972).
    [Crossref]
  3. R. V. Pole, S. E. Miller, J. H. Harris, P. K. Tien, Appl. Opt. 11, 1675 (1972).
    [Crossref] [PubMed]
  4. P. K. Tien, Appl. Opt. 10, 2395 (1971).
    [Crossref] [PubMed]
  5. P. K. Tien, R. Ulrich, J. Opt. Soc. Am. 60, 1325 (1970); P. K. Tien, R. Ulrich, R. J. Martin, Appl. Phys. Lett. 14, 291 (1969).
    [Crossref]
  6. R. Ulrich, R. J. Martin, Appl. Opt. 10, 2077 (1971).
    [Crossref] [PubMed]
  7. P. K. Tien, R. J. Martin, Appl. Phys. Lett. 18, 398 (1971).
    [Crossref]
  8. P. K. Tien, G. Smolinsky, R. J. Martin, Appl. Opt. 11, 637 (1972); M. J. Vasile, G. Smolinsky, J. Electrochem. Soc. 119, 451 (1972); L. F. Thompson, G. Smolinsky, J. Appl. Polymer Sci. 16, 1179 (1972).
    [Crossref] [PubMed]
  9. D. H. Hensler, J. D. Cuthbert, R. J. Martin, P. K. Tien, Appl. Opt. 10, 1037 (1971).
    [Crossref] [PubMed]
  10. J. H. McFee, Bell Laboratories, Holmdel, N.J. (unpublished).

1972 (3)

1971 (5)

1970 (1)

Blank, S. L.

P. K. Tien, R. J. Martin, R. Wolfe, R. C. LeCraw, S. L. Blank, Appl. Phys. Lett. 21, 394 (1972).
[Crossref]

Cuthbert, J. D.

Harris, J. H.

Hensler, D. H.

Kogelnik, H.

H. Kogelnik, C. V. Shank, Appl. Phys. Lett. 18, 152 (1971).
[Crossref]

LeCraw, R. C.

P. K. Tien, R. J. Martin, R. Wolfe, R. C. LeCraw, S. L. Blank, Appl. Phys. Lett. 21, 394 (1972).
[Crossref]

Martin, R. J.

McFee, J. H.

J. H. McFee, Bell Laboratories, Holmdel, N.J. (unpublished).

Miller, S. E.

Pole, R. V.

Shank, C. V.

H. Kogelnik, C. V. Shank, Appl. Phys. Lett. 18, 152 (1971).
[Crossref]

Smolinsky, G.

Tien, P. K.

Ulrich, R.

Wolfe, R.

P. K. Tien, R. J. Martin, R. Wolfe, R. C. LeCraw, S. L. Blank, Appl. Phys. Lett. 21, 394 (1972).
[Crossref]

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Figures (10)

Fig. 1
Fig. 1

Schematic drawing showing an arrangement of the films used in the experiment in which film G provides a light-guiding interconnection between two films L and M. Films L and M represent, respectively, the output terminal of a laser and the input terminal of a modulator in an integrated optical circuit.

Fig. 2
Fig. 2

The streaks in the photographs demonstrate that a light wave can propagate successfully through an interconnection arrangement shown in Fig. 1. The top and bottom photographs are for the m = 0 and m = 1 waveguide modes, respectively, as described in the first experiment, Sec. II of this paper. In this experiment, nL = nM = 1.567; nG = 1.539; WL = WM = 1.40 μm; WG = 1.05 μm.

Fig. 3
Fig. 3

The top photograph shows four pairs of interference fringes formed in the four tapered sections of the films in the arrangenent shown in Fig. 1. The distance between two fringes in any pair indicates roughly the length of the taper. The streaks in the two lower photographs show a light wave passing smoothly through these tapered sections. The top photograph is taken with a beam of white light on, the middle photograph with both white and laser lights on, and the bottom photograph with the laser light on only, as described in the second experiment, Sec. II of this paper. In this experiment, nL = nM = 1.539; nG = 1.567; WL = WM = 0.34 μm; WG = 0.23 μm.

Fig. 4
Fig. 4

In the top photograph, a light wave in the m = 0 mode travels successfully through the film arrangement shown in Fig. 1, whereas in the bottom photograph, a light wave in the m = 1 mode stops in the middle of the slide. The light stops as it enters the interconnection, which is not thick enough to support this waveguide mode as described in the third experiment, Sec. II of this paper. In this experiment, nL = nM = 1.539; nG = 1.567; WL = WM = 1.17 μm; WG = 0.408 μm.

Fig. 5
Fig. 5

The top photograph shows interference fringes observed at the tapered edges of Ta2O5 and TRMS films in the arrangement described in the fourth experiment, Sec. II of this paper. In spite of the large differences in refractive indices between Ta2O5 and TRMS, the streak in the bottom photograph demonstrates that light energy can still be transported between two Ta2O5 films through a TRMS interconnection. In this experiment, nL = nM = 2.060; nG = 1.569; WL = WM = 0.22 μm; WG = 1.07 μm.

Fig. 6
Fig. 6

Schematic drawing showing a composite waveguide consisting of two layers of films A and C.

Fig. 7
Fig. 7

The diagrams show distributions of Ey in a composite waveguide (nA = 1.5906; nC = 1.5218; n0 = 1.4704; n2 = 1.00; WA = 3.90 μm; WC = 1.45 μm). (a) The field distribution is sinusoidal in film A and exponential in film C. This corresponds to the case nC < β/k < nA and the particular field distribution shown is for β/k = 1.5745 and m = 3. (b) The field distribution is sinusoidal in both films A and C. This corresponds to the case n0 < β/k < nC and the particular field distribution shown is for β/k = 1.5020 and m = 7.

Fig. 8
Fig. 8

The photograph shows the m lines from a composite waveguide (nA = 1.5906; nC = 1.5218; n0 = 1.4704; n2 = 1.00; WA = 3.90 μm; WC = 1.45 μm). Each line corresponds to one waveguide mode and the lines are labeled according to the orders of the waveguide modes.

Fig. 9
Fig. 9

The top photograph shows an interferogram of a tapered film edge and the bottom photograph shows the interferogram of a uniform film. The photographs are taken with a Leitz interference microscope.

Fig. 10
Fig. 10

Diagram showing how the effective refractive index β/k of a wave varies when one follows the progress of a light wave as it transverses a composite array of waveguides and tapers such as the one shown in the bottom of the figure. The two curves are, respectively, for m = 0 and m = 1 modes of the wave propagation as described in the first experiment of Sec. II of this paper.

Tables (1)

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Table I Comparison of β/k Values

Equations (13)

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b A 2 = ( k n A ) 2 - β 2 ;
p C 2 = β 2 - ( k n C ) 2 ;
p 0 2 = β 2 - ( k n 0 ) 2 ;
p 2 2 = β 2 - ( k n 2 ) 2 .
tan ( b A W A - Φ A 2 - m A π ) = ( p C / b A ) F ,
Φ A 2 = tan - 1 ( p 2 / b A ) ;             0 < Φ A 2 < π / 2 ,
F = [ 1 - γ exp ( - 2 p C W C ) ] / [ 1 + γ exp ( - 2 p C W C ) ] ,
γ = ( p C - p 0 ) / ( p C + p 0 ) ,
b C = ( k n C ) 2 - β 2 .
b A tan ( b A W A - Φ A 2 - m A π ) = - b C tan ( b C W C - Φ C 0 - m C π ) ,
Φ C 0 = tan - 1 ( p 0 / b C ) ;             0 < Φ C 0 < π / 2.
m = m A + m C .
m = m A + m C + 1.

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