3. Silicon-Based Nano-Photonics
"A robust, efficient and miniaturized coupler module between a single-mode fiber and a silicon nano-photonic chip has been realized for applications in wideband multichannel fiber optic systems."


Silicon-based photonic nanowire waveguide structures may lead to monolithic integration among electronic, optoelectronic, and optical devices. Such Si-based integrated optoelectronic chips possess high potential for providing various optical functionalities in silicon platforms such as high-speed optical networks as well as facilitating integrated nonlinear applications. However, the great disparity in size between the mode-field diameters (MFDs) of standard single-mode fibers (SMFs) and the Si-wire waveguides will result in excessive coupling losses (higher than 25dB) when they are directly butt coupled. Clearly, a robust and efficient spot-size converter (SSC) is needed.

This joint research with Professor Kazuo Shiraishi's group at Utsunomiya University in Japan is aimed at conception and realization of such a high-performance coupler module. The SSC devised consists of a horizontal linear and a vertical nonlinear up-taper waveguides, measured 2.0 mm and 86µm in length, respectively, in cascade in a silicon-on-insulator (SOI) substrate. A SMF of diameter 5.1 x 9.2 µm2 was focused using the SSC to Si-wire waveguide diameter of 0.54 x 0.38 µm2 at a net transmission loss of 0.5 dB at the wavelength of 1.55µm. A two-port SMF-silicon wire coupler module using the above SSC, one at each port as shown in Fig.1(a), was also realized (Fig.1(b)). The total length of the two-port coupler module was as short as 1000µm. A Si-wire waveguide with diameter of 0.32x0.46 µm2 was expanded to the diameter of 2.8x8.0 µm2 at 1.55 µm wavelength with a net transmission loss of 4.1dB per port.



Fig.1(a)




Fig.1(b)

  • Selected Recent Publications

    1. "A Polarizer Using Thin Metallic-Film Sub-Wavelength Grating for Infrared to Terahertz Region," K. Shiraishi, S. Ogama, and C.S. Tsai (IEEE J. Lightwave Technology, 29, NO. 5, 670-676, 2011).
    2. "A Two-Port Single-Mode Fiber-Silicon Wire Waveguide Coupler Module Using Spot-Size Converters," H. Yoda, K. Shiraishi, A. Ohshima, T. Ishimura, H. Furuhashi, H. Tsuchiya, and C.S. Tsai, J. of Lightwave Technology, 27, 1315-1319, May 15, 2009.
    3. "Single-mode Fiber with a Plano-Convex Silicon Microlens for an Integrated Butt-Coupling Scheme," K.Shiraishi, M.Kagaya, K.Muro, H.Yoda, Y.Kogami, and C.S.Tsai, Appl. Opts., 47, 6345-6349, Dec. 1, 2008.
    4. "A Silicon-Based Spot-Size Converter between Single-Mode Fibers and Si-Wire Waveguide using Cascaded Tapers," K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C.S. Tsai, Applied Physics Letters, 91, Oct. 1, 141120, 2007.
    5. "A High-Performance Micro-GRIN-Chip Spot-Size Converter Formed with Focused Ion Beam," H.Yoda, H.Ikeda, T.Ketsuka, A.Irie, K.Shiraishi, and C.S.Tsai, IEEE Phoonics Tech. Letters, 18, 1554-1556, July 15, 2006.
    6. "A Micro Light Beam Spot-Size Converter using A Hemicylindrical GRIN-Slab Tip with High-Index Contrast," K.Shiraishi and C.S. Tsai, J. Lightwave Tech., 11, 3821-3826, Nov. 2005.
    Last revision: 1/2011. Site designed by James Dolas and Yun Zhu.