Abstract

Microscopic lenses, fabricated on optical fiber surfaces, have quadrupled the efficiency for coupling astigmatic beams from GaAs junction lasers into 4-μm cores of single-mode fibers. A novel photolithographic technique was used to make hemispherical and hemicylindrical microlenses, with diameters between 4 μm and 10 μm, from commercially available negative type photoresist that is transparent at ir laser wavelengths. Geometrical profiles of photoresist lenses, documented with scanning electron photomicrographs, were remarkably smooth even though their dimensions were more than an order of magnitude smaller than other known lenses.

© 1974 Optical Society of America

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References

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  1. L. G. Cohen, Bell Syst. Tech. J. 51, 573 (1972).
  2. A. R. McCormick, Bell Labs., Holmdel, N.J.; unpublished work.
  3. H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).
  4. W. O. Schlosser, Bell Labs., Murray Hill, N.J.; unpublished work.
  5. D. Marcuse, Light Transmission Optics (Van Nostrand Reinhold, New York, 1972), Chap. 8.
  6. H. Kogelnik, “Coupling and Conversion Coefficients for Optical Modes,” in Proceedings of the Symposium on Quasi-Optics, J. Fox, Ed. (Polytechnic Press, Brooklyn, 1964).
  7. R. E. Kerwin, Bell Labs., Murray Hill, N.J.; personal communication.

1972 (1)

L. G. Cohen, Bell Syst. Tech. J. 51, 573 (1972).

1971 (1)

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Butler, J. K.

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Cohen, L. G.

L. G. Cohen, Bell Syst. Tech. J. 51, 573 (1972).

Ettenberg, M.

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Hawrylo, F. Z.

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Kerwin, R. E.

R. E. Kerwin, Bell Labs., Murray Hill, N.J.; personal communication.

Kogelnik, H.

H. Kogelnik, “Coupling and Conversion Coefficients for Optical Modes,” in Proceedings of the Symposium on Quasi-Optics, J. Fox, Ed. (Polytechnic Press, Brooklyn, 1964).

Kressel, H.

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Lockwood, H. F.

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Marcuse, D.

D. Marcuse, Light Transmission Optics (Van Nostrand Reinhold, New York, 1972), Chap. 8.

McCormick, A. R.

A. R. McCormick, Bell Labs., Holmdel, N.J.; unpublished work.

Schlosser, W. O.

W. O. Schlosser, Bell Labs., Murray Hill, N.J.; unpublished work.

Bell Syst. Tech. J. (1)

L. G. Cohen, Bell Syst. Tech. J. 51, 573 (1972).

RCA Rev. (1)

H. Kressel, J. K. Butler, F. Z. Hawrylo, H. F. Lockwood, M. Ettenberg, RCA Rev. 32, 393 (1971).

Other (5)

W. O. Schlosser, Bell Labs., Murray Hill, N.J.; unpublished work.

D. Marcuse, Light Transmission Optics (Van Nostrand Reinhold, New York, 1972), Chap. 8.

H. Kogelnik, “Coupling and Conversion Coefficients for Optical Modes,” in Proceedings of the Symposium on Quasi-Optics, J. Fox, Ed. (Polytechnic Press, Brooklyn, 1964).

R. E. Kerwin, Bell Labs., Murray Hill, N.J.; personal communication.

A. R. McCormick, Bell Labs., Holmdel, N.J.; unpublished work.

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Figures (9)

Fig. 1
Fig. 1

Arrangement for coupling light power from a junction laser across a small air gap into the core of a single mode fiber. (a) The fiber has a microlens over its core; (b) the laser has a microlens over its active layer.

Fig. 2
Fig. 2

Experimental arrangement for automatically exposing a hemispherical lens over the core of a single mode fiber. The photograph shows a 7-μm diam microlens in perspective with the fiber cladding diameter of 250 μm.

Fig. 3
Fig. 3

Scanning electron beam photomicrographs of two different hemispherical lenses. (a) Diameter = 4.2 μm, thickness 1.8 μm; (b) diameter = 6.4 μm, thickness 2.6 μm.

Fig. 4
Fig. 4

Experimental arrangement for aligning and exposing hemicylindrical lenses over the core of a single mode fiber. The photograph shows a 7-μm × 35-μm microlens in perspective with the fiber cladding diameter of 250 μm.

Fig. 5
Fig. 5

Scanning electron beam photomicrographs of cylindrical lenses (7-μm diam × 25 μm-length).

Fig. 6
Fig. 6

Experimental arrangement for projecting the near field HE11 image, transformed by a lens, onto the plane of a frosted plate. The photographs show near field images emanating from the ends of fibers. (a) HE11 image from a fiber end without a lens; (b) image transformed by a 7-μm wide hemispherical reduction lens; (c) elliptical image transformed by a 7-μm × 25-μm long cylindrical lens.

Fig. 7
Fig. 7

Recordings of light intensity vs position in the near field of a fiber end. (a) Image transformed by a 7-μm wide hemispherical reduction lens; (b) elliptical image transformed by a 7-μm 25-μm long cylindrical lens.

Fig. 8
Fig. 8

Normalized power emitted from the end of a fiber is plotted vs axial separation between the laser and the fiber. Circular data points apply to a single-mode fiber without a lens, and triangular data points apply to a fiber with a spherical lens.

Fig. 9
Fig. 9

Far field intensity patterns from a junction laser (L-424A 2); α (parallel) and α (perpendicular) are angles measured in the planes parallel and perpendicular to the junction. The dashed lines are Gaussian fits to the intensity patterns.

Tables (1)

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Table I Summary of Measurements

Equations (5)

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ω 0 x = ( 2 ) 1 / 2 / ( π λ tan α x ) .
Z 0 x = ( L / 2 ) ( 1 / n ) 52 μ m ,
κ t h = κ x κ y = 2 / [ ( ω 0 x / a ) + ( a / ω 0 x ) ] ( 1 + { ( Z 0 x λ ) / [ π ( ω 0 x 2 + a 2 ) ] } 2 ) 1 / 2 2 [ ( ω 0 y / a ) + ( a / ω 0 y ) ]
1 / ( 1 + { ( Z 0 x λ ) / [ π ( ω 0 x 2 + a 2 ) ] } 2 ) 1 / 2
ω 0 y / a 1.

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