Ultra-low-loss optical delay line on a silicon chip
Light propagation through an optical fibre causes a long, non-resonant (true) time delay used in numerous applications. In contrast to how it is deployed in optical communication systems, fibre is coiled in these applications to reduce footprint. This is a configuration better suited for a chip-based waveguide that would improve shock resistance, and afford the possibility of integration for system-on-a-chip functionality. However, integrated waveguide attenuation rates lag far behind the corresponding rates of optical fibre, featuring attenuation many orders larger. Here we demonstrate a monolithic waveguide as long as 27 m (39 m optical path length), and featuring broadband loss rate values of (0.08±0.01) dB m^(−1) measured over 7 m by optical backscatter. Resonator measurements show a further reduction of loss to 0.037 dB m^(−1), close to that of optical fibres when first considered a viable technology. Scaling this waveguide to integrated spans exceeding 250 m and attenuation rates below 0.01 dB m^(−1) is discussed.
Additional Information© 2012 Macmillan Publishers Limited. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivative Works 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ Received 15 December 2011; Accepted 30 April 2012; Published 29 May 2012. We gratefully acknowledge the Defense Advanced Research Projects Agency under the iPhOD program and the Kavli Nanoscience Institute at Caltech. H.L. thanks the Center for the Physics of Information and the help from Kiyoul Yang and Seokmin Jeon. Author contributions: All authors made important contributions to the work. H.L. performed microfabrication of devices with assistance from T.C. T.C. and H.L. performed measurements with assistance from J.L. T.C. performed modelling with assistance from H.L. and K.J.V. H.L., T.C., O.P. and K.J.V. conceived, designed and planned the experiments. All authors helped to write the paper. The authors declare no competing financial interests.
Published - Lee2012p18592Nat_Commun.pdf