Abstract

A bilevel mode converter is analyzed for providing low-loss coupling between the small fundamental mode of a silicon nanowire waveguide and the larger mode of a conventional silicon-on-insulator (SOI) rib waveguide. The bilevel converter can also be used to improve the coupling efficiency between a lensed fiber and a silicon nanowire waveguide. The mode converter consists of two tapers formed at different levels. The top taper comprises a parabolic and sine taper, which is optimized to improve the mode conversion efficiency. Numerical analyses are given by using a three-dimensional semivectorial beam propagation method. The design has good tolerance against misalignment of the two masks needed for the double etch.

© 2006 IEEE

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  1. W. Bogaerts, R. Baets, P. Dumon, V. Wiaux, S. Beckx, D. Taillaert, B. Luyssaert, J. Van Campenhout, P. Bienstman and D. Van Thourhout, "Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology", J. Lightw. Technol., vol. 23, no. 1, pp. 401-412, Jan. 2005.
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  4. V. R. Almeida, Q. Xu, C. A. Barrios and M. Lipson, "Guiding and confining light in void nanostructure", Opt. Lett., vol. 29, no. 11, pp. 1209-1211, Jun. 2004.
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  19. G. Z. Masanovic, G. T. Reed, W. Headley and B. Timotijevic, "A high efficiency input/output coupler for small silicon photonic devices", Opt. Express, vol. 13, no. 19, pp. 7374-7379, Sep. 2005.
  20. R. N. Thurston, E. Kapon and A. Shahar, "Two-dimensional control of mode size in optical channel waveguide by lateral channel tapering", Opt. Lett., vol. 16, no. 5, pp. 306-308, Mar. 1991.
  21. F. Payne, "Semiconductor optical waveguide device", U.S. Patent 6 853 775, Feb. 8, 2005.
  22. P.-L. Liu and B.-J. Li, "Semivectorial beam-propagation method for analyzing polarized modes of rib waveguides", IEEE J. Quantum Electron., vol. 28, no. 4, pp. 778-782, Apr. 1992.
  23. W. P. Huang, C. I. Xu, W. Lui and K. Yokoyama, "The perfectly matched layer boundary condition for modal analysis of optical waveguides: Leaky mode calculations", IEEE Photon. Technol. Lett., vol. 8, no. 5, pp. 652-654, May 1996.

Other

W. Bogaerts, R. Baets, P. Dumon, V. Wiaux, S. Beckx, D. Taillaert, B. Luyssaert, J. Van Campenhout, P. Bienstman and D. Van Thourhout, "Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology", J. Lightw. Technol., vol. 23, no. 1, pp. 401-412, Jan. 2005.

D. Dai and S. He, "Analysis for characteristics of bent rib waveguides", J. Opt. Soc. Amer. A, Opt. Image Sci., vol. 21, no. 1, pp. 113-121, Jan. 2004.

T. Tsuchizawa, K. Yamada, H. Fukuda, T. Watanabe, J. Takahashi, M. Takahashi, T. Shoji, E. Tamechika, S. Itabashi and H. Morita, "Microphotonics devices based on silicon microfabrication technology", IEEE J. Sel. Topics Quantum Electron., vol. 11, no. 1, pp. 232-240, Jan./Feb. 2005.

V. R. Almeida, Q. Xu, C. A. Barrios and M. Lipson, "Guiding and confining light in void nanostructure", Opt. Lett., vol. 29, no. 11, pp. 1209-1211, Jun. 2004.

Q. Xu, V. R. Almeida, R. R. Panepucci and M. Lipson, "Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material", Opt. Lett., vol. 29, no. 14, pp. 1626-1628, Jul. 2004.

D. K. Sparcin, S. J. Spector and L. C. Kimerling, "Silicon waveguide sidewall smoothing by wet chemical oxidation", J. Lightw. Technol., vol. 23, no. 8, pp. 2455-2461, Aug. 2005.

P. Dumon, W. Bogaerts, V. Wiaux, J. Wouters, S. Beckx, J. Van Campenhout, D. Taillaert, B. Luyssaert, P. Bienstman, D. Van Thourhout and R. Baets, "Low-loss SOI photonic wires and ring resonators fabricated with deep UV lithography", IEEE Photon. Technol. Lett., vol. 16, no. 5, pp. 1328-1330, May 2004.

Y. A. Vlasor and S. J. Mcnab, "Losses in single-mode silicon-on-insulator strip waveguides and bends", Opt. Express, vol. 12, no. 8, pp. 1622-1631, Apr. 2004.

J. H. Jang, W. Zhao, J. W. Bae, D. Selvanathan, S. L. Rommel and I. Adesida, "Direct measurement of nanoscale sidewall roughness of optical waveguides using an atomic force microscope", Appl. Phys. Lett., vol. 83, no. 20, pp. 4116-4118, Nov. 2003.

F. Grillot, L. Vivien, S. Laval, D. Pascal and E. Cassan, "Size influence on the propagation loss induced by sidewall roughness in ultrasmall SOI waveguides", IEEE Photon. Technol. Lett., vol. 16, no. 7, pp. 1661-1663, Jul. 2004.

W. Bogaerts, D. Taillaert and B. Luyssaert, et al. "Basic structures for photonic integrated circuits in silicon-on-insulator", Opt. Express, vol. 12, no. 8, pp. 1583-1591, Apr. 2004.

K. Sasaki, F. Ohno, A. Motegi and T. Baba, "Arrayed waveguide grating of 70 × 60 µm2 size based on silicon photonic wire waveguides", Electron. Lett., vol. 41, no. 14, pp. 801-802, Jul. 2005.

I. Day, I. Evans, A. Knights, F. Hopper, S. Roberts, J. Johnston, S. Day, J. Luff, H. Tsang and M. Asghari, "Tapered silicon waveguides for low insertion loss highly-efficient high-speed electronic variable optical attenuators", in Proc. OFC, Atlanta, GA, Mar. 2003, pp. 249-251.

D. X. Dai, J. J. He and S. L He, "Elimination of multimode effects in a silicon-on-insulator etched diffraction grating demultiplexer with bi-level taper structure", IEEE J. Sel. Topics Quantum Electron., vol. 11, no. 2, pp. 439-443, Mar./Apr. 2005.

D. Taillaert, W. Bogaerts, P. Bienstman, T. F. Krauss, P. V. Daele, I. Moerman, S. Verstuyft, K. D. Mesel and R. Baets, "An out-of-plane grating coupler for efficient butt-coupling between compact planar waveguides and single-mode fibers", IEEE J. Quantum Electron., vol. 38, no. 7, pp. 949-955, Jul. 2002.

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada and H. Morita, "Low loss mode size converter from 0.3 µm square silicon wire waveguides to single-mode fibers", Electron. Lett., vol. 38, no. 25, pp. 1669-1670, Dec. 2002.

V. R. Almeida, R. R. Panepucci and M. Lipson, "Nanotaper for compact mode conversion", Opt. Lett., vol. 28, no. 15, pp. 1302-1304, Aug. 2003.

K. K. Lee, D. R. Lim, D. Pan, C. Hoepfner, W.-Y. Oh, K. Wada, L. C. Kimerling, K. P. Yap and M. T. Doan, "Mode transformer for miniaturized optical circuits", Opt. Lett., vol. 30, no. 5, pp. 498-500, Mar. 2005.

G. Z. Masanovic, G. T. Reed, W. Headley and B. Timotijevic, "A high efficiency input/output coupler for small silicon photonic devices", Opt. Express, vol. 13, no. 19, pp. 7374-7379, Sep. 2005.

R. N. Thurston, E. Kapon and A. Shahar, "Two-dimensional control of mode size in optical channel waveguide by lateral channel tapering", Opt. Lett., vol. 16, no. 5, pp. 306-308, Mar. 1991.

F. Payne, "Semiconductor optical waveguide device", U.S. Patent 6 853 775, Feb. 8, 2005.

P.-L. Liu and B.-J. Li, "Semivectorial beam-propagation method for analyzing polarized modes of rib waveguides", IEEE J. Quantum Electron., vol. 28, no. 4, pp. 778-782, Apr. 1992.

W. P. Huang, C. I. Xu, W. Lui and K. Yokoyama, "The perfectly matched layer boundary condition for modal analysis of optical waveguides: Leaky mode calculations", IEEE Photon. Technol. Lett., vol. 8, no. 5, pp. 652-654, May 1996.

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