Bilevel mode converter between a silicon nanowire waveguide and a larger waveguide

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.

[1]  Y. Vlasov,et al.  Losses in single-mode silicon-on-insulator strip waveguides and bends. , 2004, Optics express.

[2]  Sailing He,et al.  Analysis of characteristics of bent rib waveguides. , 2004, Journal of the Optical Society of America. A, Optics, image science, and vision.

[3]  L. Vivien,et al.  Size influence on the propagation loss induced by sidewall roughness in ultrasmall SOI waveguides , 2004, IEEE Photonics Technology Letters.

[4]  P. Dumon,et al.  Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology , 2005, Journal of Lightwave Technology.

[5]  William Headley,et al.  A high efficiency input/output coupler for small silicon photonic devices. , 2005, Optics express.

[6]  Qianfan Xu,et al.  Guiding and confining light in void nanostructure. , 2004, Optics letters.

[7]  Toshihiko Baba,et al.  Arrayed waveguide grating of 70×60 µm2 size based on Si photonic wire waveguides , 2005 .

[8]  Hon Ki Tsang,et al.  Tapered silicon waveguides for low insertion loss highly-efficient high-speed electronic variable optical attenuators , 2003, OFC 2003 Optical Fiber Communications Conference, 2003..

[9]  S. Spector,et al.  Silicon waveguide sidewall smoothing by wet chemical oxidation , 2005, Journal of Lightwave Technology.

[10]  T. Tsuchizawa,et al.  Low loss mode size converter from 0.3 /spl mu/m square Si wire waveguides to singlemode fibres , 2002 .

[11]  T. Krauss,et al.  An out-of-plane grating coupler for efficient butt-coupling between compact planar waveguides and single-mode fibers , 2002 .

[12]  K. P. Yap,et al.  Mode transformer for miniaturized optical circuits. , 2005, Optics letters.

[13]  Sailing He,et al.  Elimination of multimode effects in a silicon-on-insulator etched diffraction grating demultiplexer with bi-level taper structure , 2005 .

[14]  Pao-Lo Liu,et al.  Semivectorial beam-propagation method for analyzing polarized modes of rib waveguides , 1992 .

[15]  T. Shoji,et al.  Microphotonics devices based on silicon microfabrication technology , 2005, IEEE Journal of Selected Topics in Quantum Electronics.

[16]  K. Yokoyama,et al.  The perfectly matched layer boundary condition for modal analysis of optical waveguides: leaky mode calculations , 1996, IEEE Photonics Technology Letters.

[17]  D. Van Thourhout,et al.  Low-loss SOI photonic wires and ring resonators fabricated with deep UV lithography , 2004, IEEE Photonics Technology Letters.

[18]  M. Lipson,et al.  Nanotaper for compact mode conversion. , 2003, Optics letters.

[19]  Qianfan Xu,et al.  Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material. , 2004, Optics letters.

[20]  P. Dumon,et al.  Basic structures for photonic integrated circuits in Silicon-on-insulator. , 2004, Optics express.

[21]  E Kapon,et al.  Two-dimensional control of mode size in optical channel waveguides by lateral channel tapering. , 1991, Optics letters.

[22]  Joseph H. Abeles,et al.  Direct measurement of nanoscale sidewall roughness of optical waveguides using an atomic force microscope , 2003 .