Abstract

We explore the use of air trenches to achieve compact high efficiency 90° waveguide bends and beamsplitters for waveguide material systems that have low refractive index and low refractive index contrast between the core and clad materials. For a single air interface, simulation results show that the optical efficiency of a waveguide bend can be increased from 78.4% to 99.2% by simply decreasing the bend angle from 90° to 60°. This can be explained by the angular spectrum of the waveguide mode optical field. For 90° bends we use a micro-genetic algorithm (µGA) with a 2-D finite difference time domain (FDTD) method to rigorously design high efficiency waveguide bends composed of multiple air trenches. Simulation results show an optical efficiency of 97.2% for an optimized bend composed of three air trenches. Similarly, a single air trench can be designed to function as a 90° beamsplitter with 98.5% total efficiency.

© 2003 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]

IEEE Proc. (1)

R. A. Soref, �??Silicon-based optoelectronics,�?? IEEE Proc. 81 1687 (1993).
[CrossRef]

J. Appl. Phys. (1)

A. M. Agarwal, L. Liao, J. S. Foresi, M. R. Black, X. Duan, and L. C. Kimmerling, �??Low-loss polycrystalline silicon waveguides for silicon photonics,�?? J. Appl. Phys. 80 6120 (1996).
[CrossRef]

J. Comput. Phys. (1)

J. P. Berenger, �??A perfectly matched layer for the absorption of electromagnetic waves,�?? J. Comput. Phys. 114, 185-200 (1994).
[CrossRef]

J. Lightwave Technol. (2)

Chulhun Seo, Jerry C. Chen, �??Low transition losses in bent rib waveguides,�?? J. Lightwave Technol. 14 2255-2259 (1996).
[CrossRef]

R. Orobtchouk, S. Laval, D. Pascal, A. Koster, �??Analysis of Integrated Optical Waveguide Mirrors,�?? J. Lightwave Technol. 15 815-820 (1997).
[CrossRef]

J. of Lightwave Technol. (1)

C. Manolatou, S.G. Johnson, S. Fan, P.R. Villeneuve, H. A. Haus, and J. D. Joannopoulus, �??High-Density Integrated Optics,�?? J. of Lightwave Technol., 17 1682-1692 Sept. (1999).
[CrossRef]

J. Quantum Electron. (1)

R. A. Soref, J. Schmidtchen, and K. Petermann, �??Large single-mode rib waveguides in GeSi-Si and Si-on-SiO2,�?? J. Quantum Electron. 27 1971 (1991).
[CrossRef]

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

L. Eldada and L. W. Shacklette, �??Advances in polymer integrated optics,�?? J. Sel. Top. Quantum Electron. 6 54 (2000).
[CrossRef]

Opt. Express (2)

J. Jiang and G. Nordin, �??A rigorous unidirectional method for designing finite aperture diffractive optical elements,�?? Opt. Express 7, 237-242 (2000). <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-7-6-237">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-7-6-237</a>
[CrossRef] [PubMed]

R.L. Espinola, R.U. Ahmad, F. Pizzuto, M.J. Steel and R.M. Osgood, Jr., �??A study of high-index-contrast 90o waveguide bend structures,�?? Opt. Express 8, 517-528 (2001), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-8-9-517">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-8-9-517</a>
[CrossRef] [PubMed]

Opt. Lett. (1)

Phot. Techn. Lett. (4)

John E. Johnson, C.L. Tang, �??Precise determination of turning mirror loss using GaAs/AlGaAs lasers with up to ten 90o intracavity turning mirrors,�?? Phot. Techn. Lett. 4 24-26 (1992).
[CrossRef]

P. D. Swanson, D. B. Shire, C. L. Tang, M. A. Parker, J. S. Kimmet and R. J. Michlak, �??Electron-cyclotron resonance etching of mirrors for ridge-guided lasers,�?? Phot. Techn. Lett. 7 605-607 (1995).
[CrossRef]

U. Fischer, T. Zinke, J.-R. Kropp, F. Arndt, and K. Petermann, �??0.1 dB/cm waveguide losses in singlemode SOI rib waveguides,�?? Phot. Techn. Lett. 8 647 (1996).
[CrossRef]

Y. Z. Tang, W. H. Wang, etc., �??Integrated waveguide turning mirror in silicon-on insulator,�?? Phot. Techn. Lett. 14 68-70, Jan. (2002).
[CrossRef]

Other (3)

K. Wada, M. Popovic, S. Akiyama, H. A. Haus, J. Michel, �??Micron-size bending radii in silica-based waveguides,�?? Advanced Semiconductor Lasers and Applications/ Ultraviolet and Blue Lasers and Their Applications /Ultralong Haul DWDM Transmission and Networking/WDM Components, 2001. Digest of the LEOS Summer Topical Meetings, (Copper Mountain, CO USA, 2001), 13-14.

M. V. Klein and T. E. Furtak, Optics, 2nd Ed. (John Wiley and Sons, New York, 1986).

A. Taflove, Computational Electrodynamics: The Finite-Difference Time-Domain Method, (Artech House, Boston, Mass.,1995).

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Figures (8)

Fig.1.
Fig.1.

Schematic diagram of bend angle definition and a 90° waveguide bend formed by an air interface.

Fig. 2.
Fig. 2.

FDTD simulation result for a 90° bend. The colormap is the same for Figs. 4, 5, and 8(a).

Fig. 3.
Fig. 3.

(a) Waveguide mode profile and (b) its angular spectrum.

Fig. 4.
Fig. 4.

FDTD simulation results for (a) 80° and (b) 60° bends.

Fig. 5.
Fig. 5.

Micro-genetic algorithm-optimized air-trench structures for (a) one, (b) two, and (c) three layers.

Fig. 6.
Fig. 6.

Bend efficiency dependence on wavelength for the 90° air-trench bends of Fig. 5.

Fig. 7.
Fig. 7.

Air-trench beamsplitter. (a) Time-average square magnitude of electric field (monochromatic source at 1.55 µm) and (b) temporal snapshot of the electric field for a pulsed source.

Fig. 8.
Fig. 8.

Air-trench beamsplitter transmission and reflection efficiency.

Tables (1)

Tables Icon

Table 1. Geometry and performance of air-trench 90° bends.

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