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Localization in silicon nanophotonic slow-light waveguides


Slowing down light on a chip can lead to the development of optical buffers1, filters2,3 and memory elements4 useful for optical interconnects and for resonantly enhanced chip-based nonlinear optics5,6. Several approaches to slow light rely on the phenomenon of light interference in a sequence of coupled resonators1,2,3,4,7,8,9,10,11; however, light interference is also responsible, in disordered structures, for the localization of light, an effect particularly prominent in one-dimensional devices12,13. Until now, the length of the waveguides investigated has been less than the localization length. Here we report the first observation of light localization in compact silicon nanophotonic slow-light waveguides consisting of long sequences of coupled resonators. Our results show that disorder limits how much light can be slowed, and that localization leads to spatially concentrated and locally trapped light in a quasi-one-dimensional waveguide at wavelengths near the band edge.

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Figure 1: Dispersion and density of states for a weakly disordered slow-wave structure.
Figure 2: Spectral distribution of localization.
Figure 3: Slow-wave coupled-resonator waveguides.
Figure 4: Experimental measurements of localization.


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This work was supported by the US National Science Foundation under grants ECCS-0642603 and ECCS-0403589. J.P. acknowledges sponsorship support provided by the National Science Graduate Student Fellowship. The authors are grateful to the San Diego Supercomputer Center for computational resources, and to Y. Fainman for making his lapping machine available to us. A. Oh provided assistance with numerical simulations.

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S.M. contributed to all aspects of the project. J.S.P. contributed to experimental work and data analysis. S.H.Y. and P.B. contributed materials. All authors contributed to discussing the results and writing the paper.

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Correspondence to Shayan Mookherjea.

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Mookherjea, S., Park, J., Yang, SH. et al. Localization in silicon nanophotonic slow-light waveguides. Nature Photon 2, 90–93 (2008).

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