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11 October 2013 Metamaterial Lüneburg waveguide lenses for switch fabric on-a-chip applications
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Proceedings Volume 8915, Photonics North 2013; 89150O (2013)
Event: Photonics North 2013, 2013, Ottawa, Canada
Optical information processing has traditionally been demonstrated using 3D free-space optical systems employing bulk optical components. These systems are bulky and unstable due to the stringent alignment tolerances that must be met. Taking advantage of the alignment accuracy offered by planar light circuits, these issues may be overcome by confining the light in a planar slab waveguide. The limitation on scaling, consequent on the loss of one dimension is offset by the nanoscale component footprints attainable in a silicon integration platform. A key component of this free-space-opticson- a-chip concept is a waveguide lens. Waveguide lenses are of general utility but our specific application is their use to implement the complex crossover interconnections of a switch fabric. The graded refractive index of the lens is engineered by patterning the silicon layer of silicon on insulator slab waveguides into a dense distribution of cylinders; either solid (silicon) or voids (air); using a single etch step. The cylinders have variable diameters and are placed on a regular square or hexagonal grid with sub-wavelength pitch. In the case of voids, the patterned silicon may be suspended in air to form the core of a symmetric slab waveguide. Solid cylinders must be supported by the Si02 layer leading to an asymmetric waveguide of reduced effective index range. Advantageously, the patterning of the metamaterial region within the slab-waveguide requires only a single etch step. Photonic wire feeder waveguides at different positions around the lens may be used to launch light into the lenses or collect light from the lenses. A method is developed to determine the local effective media index of a periodic metamaterial in terms of the parameters of its unit cell. This method is used as a calibration to lay out a metamaterial with graded parameters. The operation of a metamaterial Lüneburg lens telescope is verified by FDTD simulations and shown to be capable of near zero insertion loss and crosstalk. The careful approximation of the graded index of the Lüneburg lens by a metamaterial introduces minimal impairments.
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H. Nikkhah, A. Benhsaien, R. Maldonado-Basilio, S. Abdul-Majid, and T. J. Hall "Metamaterial Lüneburg waveguide lenses for switch fabric on-a-chip applications", Proc. SPIE 8915, Photonics North 2013, 89150O (11 October 2013);

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