Abstract

We present the fabrication of 3D adiabatically tapered structures, for efficient coupling from an optical fiber, or free-space, to a chip. These structures are fabricated integrally with optical waveguides in a silicon-on-insulator wafer. Fabrication involves writing a single grayscale mask in HEBS glass with a high-energy electron beam, ultra-violet grayscale lithography, and inductively coupled plasma etching. We also present the experimentally determined coupling efficiencies of the fabricated tapers using end-fire coupling. The design parameters of the tapered structures are based on electromagnetic simulations and are discussed in this paper.

© 2003 Optical Society of America

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References

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  1. T. Tamir: Integrated Optics, 2nd Topics Appl. Phys. 7 (Springer, Berlin Heidelberg, New York, 1979) Chap. 1.
  2. <a href="http://www.corning.com">http://www.corning.com</a>
  3. Zhaolin Lu, Peng Yao, David Pustai, Janusz Murakowski, and Dennis W. Prather, �??Silicon-Prism Coupling into 260nm-SOI Slab Waveguides,�?? Opt. Lett. (Accepted).
  4. R. Hunsperger, Integrated Optics: Theory and Technology (Springer-Verlag, 1995).
  5. H. M. Presby and C. A. Edwards, �??Near 100% efficient fiber microlenses,�?? Electron. Lett. 28, 582-584 (1992).
    [CrossRef]
  6. T. Brenner, W. Hunziker, M. Smit, M. Bachmann, G. Guekos, and H. Melchior, �??Vertical InP/InGasAsP tapers for low-loss optical fiber-waveguide coupling,�?? Electron. Lett. 28, 2040-2041 (1992).
    [CrossRef]
  7. M. Chien, U. Koren, T. L. Koch, B. I. Miller, M. G. Young, M. Chien, and G. Raybon, "Short cavity distributed Bragg reflector laser with an integrated tapered output waveguide," IEEE Photon. Technol. Lett. 3, 418-420 (1991).
    [CrossRef]
  8. T. Brenner and H. Melchior, "Integrated Optical Modeshape Adapters in InGaAsP/InP for efficient Fiber-to-Waveguide Coupling," IEEE Photon. Technol. Lett. 5, 1053-1056 (1993).
    [CrossRef]
  9. G. Muller, G. Wender, L. Stoll, H. Westermeier, and D. Seeberger, "Fabrication techniques for vertically tapered InP/InGasAsP spot-size transformers with very low loss," presented at Proc. Eur. conf. Integrated Optics, Neuchatel, Switzerland, 1993.
  10. B. Jacobs, R. Zengerle, K. Faltin, and W. Weiershausen, "Vertically tapered spot size transformers by a simple masking technique," Electron. Lett. 31, 794-796, (1995).
    [CrossRef]
  11. Ingrid Moerman, Peter P. Van Daele, and P. M. Demeester, "A Review on Fabrication Technologies for the Monolithic Integration of Tapers with III-V Semiconductor Devices," IEEE J. Sel. Top. Quantum Electron. 3, 1308-1320 (1997).
    [CrossRef]
  12. R. S. Fan and B. Hooker, "Tapered Polymer Single-Mode Waveguides for Mode Transformation," IEEE J. Lightwave Technol. 17, 466-474 (1990).
    [CrossRef]
  13. <a href="http://www.confluentphotonics.com/technology/technical_papers.php#fabrication">http://www.confluentphotonics.com/technology/technical_papers.php#fabrication</a>
  14. J. J. Fijol, E. E. Fike, P. B. Keating, D. Gilbody, J. LeBlanc, S. A. Jacobson, W. J. Kessler, and M. B. Frish, "Fabrication of silicon-on-insulator adiabatic tapers for low loss optical interconnection of photonic devices," presented at the Photonics West, San Jose, California, USA, 25-31 Jan. 2003.
  15. D. W. Prather, J. Murakowski, S. Shi, S. Venkataraman, A. Sharkawy, CH. Chen, D. Pustai, "High efficiency coupling structure for a single-line defect photonic-crystal waveguide," Opt. Lett. 1601-1603 (2002).
    [CrossRef]
  16. G. R. Hadley, "Design of tapered waveguides for improved output coupling," IEEE Photon. Technol. Lett. 5, 892-894 (1993).
  17. Dominic F G Gallagher and T. P. Felici, "Eigen Mode Expansion_ A Powerful Computational Method for the Rigorous Solution of Optical Propagation Problems," in Business Briefing: Global Optical Communications, 1-6 (2002).
  18. C. Wu, �??High Energy Beam Sensitive Glasses,�?? February 1994. U.S. Patent 5,285,517.
  19. Thomas Dillon, Anita Sure, Janusz Murakowski and Dennis W. Prather, �??Continuous-tone grayscale mask fabrication using high-energy-beam-sensitive glass," (To be published).
  20. Thomas Dillon, Anita Sure, Janusz Murakowski and Dennis W. Prather, �??Process development and application of grayscale lithography for efficient three-dimensionally profiled fiber-to-waveguide couplers,�?? Proceedings of SPIE, 5183 (2003).
  21. Marion LeCompte, Xiang Gao, and Dennis W. Prather, �??Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements,�?? Appl. Opt. 40, 5291-5927 (2001).
    [CrossRef]
  22. C. Gimkiewicz, D. Hagedorn, J. Jahns, E. B. Kley, and F. Thoma, "Fabrication of micro prisms for planar optical interconnections by use of analog gray-scale lithography with high-energy-beam-sensitive glass," Appl. Opt. 38, 2986-2990 (1999).
    [CrossRef]

Appl. Opt. (2)

Marion LeCompte, Xiang Gao, and Dennis W. Prather, �??Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements,�?? Appl. Opt. 40, 5291-5927 (2001).
[CrossRef]

C. Gimkiewicz, D. Hagedorn, J. Jahns, E. B. Kley, and F. Thoma, "Fabrication of micro prisms for planar optical interconnections by use of analog gray-scale lithography with high-energy-beam-sensitive glass," Appl. Opt. 38, 2986-2990 (1999).
[CrossRef]

Business Briefing: Global Optical Commun (1)

Dominic F G Gallagher and T. P. Felici, "Eigen Mode Expansion_ A Powerful Computational Method for the Rigorous Solution of Optical Propagation Problems," in Business Briefing: Global Optical Communications, 1-6 (2002).

Electron. Lett. (3)

B. Jacobs, R. Zengerle, K. Faltin, and W. Weiershausen, "Vertically tapered spot size transformers by a simple masking technique," Electron. Lett. 31, 794-796, (1995).
[CrossRef]

H. M. Presby and C. A. Edwards, �??Near 100% efficient fiber microlenses,�?? Electron. Lett. 28, 582-584 (1992).
[CrossRef]

T. Brenner, W. Hunziker, M. Smit, M. Bachmann, G. Guekos, and H. Melchior, �??Vertical InP/InGasAsP tapers for low-loss optical fiber-waveguide coupling,�?? Electron. Lett. 28, 2040-2041 (1992).
[CrossRef]

IEEE J. Lightwave Technol. (1)

R. S. Fan and B. Hooker, "Tapered Polymer Single-Mode Waveguides for Mode Transformation," IEEE J. Lightwave Technol. 17, 466-474 (1990).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron. (1)

Ingrid Moerman, Peter P. Van Daele, and P. M. Demeester, "A Review on Fabrication Technologies for the Monolithic Integration of Tapers with III-V Semiconductor Devices," IEEE J. Sel. Top. Quantum Electron. 3, 1308-1320 (1997).
[CrossRef]

IEEE Photon. Technol. Lett. (3)

M. Chien, U. Koren, T. L. Koch, B. I. Miller, M. G. Young, M. Chien, and G. Raybon, "Short cavity distributed Bragg reflector laser with an integrated tapered output waveguide," IEEE Photon. Technol. Lett. 3, 418-420 (1991).
[CrossRef]

T. Brenner and H. Melchior, "Integrated Optical Modeshape Adapters in InGaAsP/InP for efficient Fiber-to-Waveguide Coupling," IEEE Photon. Technol. Lett. 5, 1053-1056 (1993).
[CrossRef]

G. R. Hadley, "Design of tapered waveguides for improved output coupling," IEEE Photon. Technol. Lett. 5, 892-894 (1993).

Opt. Lett. (2)

Zhaolin Lu, Peng Yao, David Pustai, Janusz Murakowski, and Dennis W. Prather, �??Silicon-Prism Coupling into 260nm-SOI Slab Waveguides,�?? Opt. Lett. (Accepted).

D. W. Prather, J. Murakowski, S. Shi, S. Venkataraman, A. Sharkawy, CH. Chen, D. Pustai, "High efficiency coupling structure for a single-line defect photonic-crystal waveguide," Opt. Lett. 1601-1603 (2002).
[CrossRef]

Photonics West (1)

J. J. Fijol, E. E. Fike, P. B. Keating, D. Gilbody, J. LeBlanc, S. A. Jacobson, W. J. Kessler, and M. B. Frish, "Fabrication of silicon-on-insulator adiabatic tapers for low loss optical interconnection of photonic devices," presented at the Photonics West, San Jose, California, USA, 25-31 Jan. 2003.

Proc. Eur. conf. Integrated Optics (1)

G. Muller, G. Wender, L. Stoll, H. Westermeier, and D. Seeberger, "Fabrication techniques for vertically tapered InP/InGasAsP spot-size transformers with very low loss," presented at Proc. Eur. conf. Integrated Optics, Neuchatel, Switzerland, 1993.

Proceedings of SPIE (1)

Thomas Dillon, Anita Sure, Janusz Murakowski and Dennis W. Prather, �??Process development and application of grayscale lithography for efficient three-dimensionally profiled fiber-to-waveguide couplers,�?? Proceedings of SPIE, 5183 (2003).

Topics Appl. Phys. (1)

T. Tamir: Integrated Optics, 2nd Topics Appl. Phys. 7 (Springer, Berlin Heidelberg, New York, 1979) Chap. 1.

Other (5)

<a href="http://www.corning.com">http://www.corning.com</a>

R. Hunsperger, Integrated Optics: Theory and Technology (Springer-Verlag, 1995).

C. Wu, �??High Energy Beam Sensitive Glasses,�?? February 1994. U.S. Patent 5,285,517.

Thomas Dillon, Anita Sure, Janusz Murakowski and Dennis W. Prather, �??Continuous-tone grayscale mask fabrication using high-energy-beam-sensitive glass," (To be published).

<a href="http://www.confluentphotonics.com/technology/technical_papers.php#fabrication">http://www.confluentphotonics.com/technology/technical_papers.php#fabrication</a>

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Figures (9)

Fig. 1.
Fig. 1.

Grayscale device fabrication steps.

Fig. 2.
Fig. 2.

Design of the test structure.

Fig. 3.
Fig. 3.

Variation of the efficiency versus taper length (calculated using BPM).

Fig. 4.
Fig. 4.

Design and fabrication of a grayscale HEBS glass mask. A. Schematic representation of the mask exposure; the mask material darkens in response to energetic beam. B. Calibration of the mask response in net optical density as a function of exposure dose. From these curves, required dose is backed out to achieve desired glass darkening for tapers. C. Optical density map of the tapered couplers. D. Cross section of taper highlighted in C.

Fig. 5.
Fig. 5.

SEM viewgraph of the tapered couplers realized in photoresist.

Fig. 6.
Fig. 6.

SEM viewgraph of the Tapered couplers etched into silicon.

Fig. 7.
Fig. 7.

Experimental setup used to characterize the couplers.

Fig. 8.
Fig. 8.

Mode profile observed at the output facet of the symmetric couplers. The height of the central waveguide, in microns, is indicated near the images. The appearance of the circular mode for the 2 and 0.5µm waveguide implies that the coupler is maintaining the single mode behavior. However, for the 0.25µm waveguide, higher order modes also exist. The mode profile of the straight waveguide is also shown for comparison.

Fig. 9.
Fig. 9.

Experimental coupling efficiency of the symmetric couplers calculated with respect to a concurrently fabricated straight waveguide.

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