• Title : Ultracompact Photonic-Waveguide Circuits in Si-Pillar Photonic-Crystal Structures for Integrated Nanophotonic Switches
• Author : M. Tokushima, J. J. Vegas Olmos, K. Kitayama
• Journal : Journal of Nanoscience and Nanotechnology, Vol.10, No.3, pp.1626-1634, March 2010.
• Abstract : Highly integrated optical device technology based on square-lattice Si- pillar photonic-crystal-(PC) waveguides is described. The Si-pillar PC waveguides are now ready to use, since efficient optical coupling structures to Si-wire waveguides have been devised. Nanophotonic switches using the Si-pillar-PC waveguides were experimentally demonstrated. The nanophotonic switches make use of two of the features of Si-pillar photonic crystal waveguides. One is the property of slow-light and the other is the usability of zero-radius 90�‹ bends, both of which enable waveguide-based optical devices to be greatly miniaturized. Even apart from the cut-off wavelength, the group index of the pillar-PC waveguides was about 7.8, which was about twice that of a Si-wire waveguide for the entire C-band of telecommunications wavelengths. The 3-dB couplers we fabricated were only 3.2-ƒÊm long thanks to the 90�‹ sharp bends, and they operated throughout the entire C-band. Waveguide-cross operation was also demonstrated in the entire C-band. Asymmetric Mach-Zehnder interferometers (MZIs) were configured by using the 3-dB couplers in an area of 13.2 �~ 37.2 ƒÊm. An MZI with a Si-wire heater successfully operated with an extinction ratio of about 20 dB at a heating power of 17 mW. It is strongly suggested that Si-pillar PC photonic-waveguide technology should help us to achieve densely integrated optical-matrix switches demanded for future photonic- telecommunication systems.

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